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Last Updated :2024/10/09

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Master

Affiliation (Master)

  • Faculty of Science　Physics　Nonlinear Physics

Affiliation (Master)

  • Faculty of Science　Physics　Nonlinear Physics

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Profile and Settings

Degree

  • Doctor(Science)（The University of Tokyo）

Profile and Settings

  • Name (Japanese)

    Sorai

  • Name (Kana)

    Kazuo

  • Name

    200901021841688126

Achievement

Research Interests

  • 電波天文学   星間物理学   銀河物理学   Radio Astronomy   Interstellar Physics   Galactic Astronomy   

Research Areas

  • Natural sciences / Astronomy

Research Experience

  • 2021/04 - Today Hokkaido University Faculty of Science Professor
  • 2021/10 - 2024/03 University of Tsukuba Faculty of Pure and Applied Sciences Professor (cross appointment)
  • 2017/04 - 2021/09 University of Tsukuba Faculty of Pure and Applied Sciences Associate Professor (cross appointment)
  • 2012/04 - 2021/03 Hokkaido University Faculty of Science Associate Professor
  • 2007/04 - 2012/03 Hokkaido University Faculty of Science Assistant Professor
  • 2006/04 - 2007/03 Hokkaido University Faculty School of Science Research Associate
  • 2002/05 - 2006/03 Hokkaido University Graduate School of Science Research Associate

Published Papers

  • Atsushi Yasuda, Nario Kuno, Kazuo Sorai, Kazuyuki Muraoka, Yusuke Miyamoto, Hiroyuki Kaneko, Yoshiyuki Yajima, Takahiro Tanaka, Kana Morokuma-Matsui, Tsutomu T Takeuchi, Masato I N Kobayashi
    Publications of the Astronomical Society of Japan 2023/06/10
  • Yoshiyuki Yajima, Kazuo Sorai, Yusuke Miyamoto, Kazuyuki Muraoka, Nario Kuno, Hiroyuki Kaneko, Tsutomu T Takeuchi, Atsushi Yasuda, Takahiro Tanaka, Kana Morokuma-Matsui, Masato I N Kobayashi
    Publications of the Astronomical Society of Japan 73 (2) 257 - 285 0004-6264 2021/04/05 [Refereed]
     
    Abstract While molecular gas mass is usually derived from 12CO(J = 1–0)—the most fundamental line for exploring molecular gas—it is often derived from 12CO(J = 2–1) assuming a constant 12CO(J = 2–1)$/$12CO(J = 1–0) line ratio (R2/1). We present variations of R2/1 and effects of the assumption that R2/1 is a constant in 24 nearby galaxies using 12CO data obtained with the Nobeyama 45 m radio telescope and IRAM 30 m telescope. The median of R2/1 for all galaxies is 0.61, and the weighted mean of R2/1 by 12CO(J = 1–0) integrated intensity is 0.66 with a standard deviation of 0.19. The radial variation of R2/1 shows that it is high (∼0.8) in the inner ∼1 kpc while its median in disks is nearly constant at 0.60 when all galaxies are compiled. In the case that the constant R2/1 of 0.7 is adopted, we found that the total molecular gas mass derived from 12CO(J = 2–1) is underestimated/overestimated by ∼20%, and at most by 35%. The scatter of molecular gas surface density within each galaxy becomes larger by ∼30%, and at most by 120%. Indices of the spatially resolved Kennicutt–Schmidt relation by 12CO(J = 2–1) are underestimated by 10%–20%, at most 39%, in 17 out of 24 galaxies. R2/1 has good positive correlations with star-formation rate and infrared color, and a negative correlation with molecular gas depletion time. There is a clear tendency of increasing R2/1 with increasing kinetic temperature (Tkin). Further, we found that not only Tkin but also pressure of molecular gas is important in understanding variations of R2/1. Special considerations should be made when discussing molecular gas mass and molecular gas properties inferred from 12CO(J = 2–1) instead of 12CO(J = 1–0).
  • P. Andreani, Y. Miyamoto, H. Kaneko, A. Boselli, K. Tatematsu, K. Sorai, R. Vio
    Astronomy & Astrophysics 643 L11 - L11 0004-6361 2020/11 [Refereed]
     
    Aims. We construct the molecular mass function using the bivariate K-band-mass function (BMF) of the Herschel Reference Survey (HRS), which is a volume-limited sample that has already been widely studied at the entire electromagnetic spectrum. Methods. The molecular mass function was derived from the K-band and the gas mass cumulative distribution using a copula method, which is described in detail in our previous papers. Results. The H2 mass is relatively strongly correlated with the K-band luminosity because of the tight relation between the stellar mass and the molecular gas mass within the sample with a scatter, which is likely due to those galaxies which have lost their molecular content because of environmental effects or because of a larger gas consumption due to past star formation processes. The derived H2 MF samples the molecular mass range from ∼4 × 106M⊙ to ∼1010 M⊙, and when compared with theoretical models, it agrees well with the theoretical predictions at the lower end of the mass values; whereas at masses larger than 1010 M⊙, the HRS sample may miss galaxies with a large content of molecular hydrogen and the outcomes are not conclusive. The value of the local density of the molecular gas mass inferred from our analysis is ∼1.5 × 107 M⊙ Mpc−3, and it is compared with the results at larger redshifts, confirming the lack of strong evolution for the molecular mass density between z = 0 and z = 4. Conclusions. This is the first molecular mass function that has been derived on a complete sample in the local Universe, which can be used as a reliable calibration at redshift z = 0 for models aiming to predict the evolution of the molecular mass density.
  • Dragan Salak, Naomasa Nakai, Kazuo Sorai, Yusuke Miyamoto
    The Astrophysical Journal 2020/10/05
  • Kana Morokuma-Matsui, Kazuo Sorai, Yuya Sato, Nario Kuno, Tsutomu T Takeuchi, Dragan Salak, Yusuke Miyamoto, Yoshiyuki Yajima, Kazuyuki Muraoka, Hiroyuki Kaneko
    Publications of the Astronomical Society of Japan 72 (5) 0004-6264 2020/10/02 [Refereed]
     
    Abstract We investigate the molecular gas properties of galaxies across the main sequence of star-forming (SF) galaxies in the local Universe using 12CO(J = 1–0), hereafter 12CO, and 13CO(J = 1–0), hereafter 13CO, mapping data of 147 nearby galaxies obtained in the COMING project, a legacy project of the Nobeyama Radio Observatory. In order to improve the signal-to-noise ratios of both lines, we stack all the pixels where 12CO emission is detected after aligning the line center expected from the first-moment map of 12CO. As a result, 13CO emission is successfully detected in 80 galaxies with a signal-to-noise ratio larger than three. The error-weighted mean of the integrated-intensity ratio of 12CO to 13CO lines (R1213) of the 80 galaxies is 10.9, with a standard deviation of 7.0. We find that (1) R1213 positively correlates to specific star-formation rate (sSFR) with a correlation coefficient of 0.46, and (2) both the flux ratio of IRAS 60 μm to 100 μm (f60/f100) and the inclination-corrected linewidth of 12CO stacked spectra ($\sigma _{ { \rm ^{12}CO},i}$) also correlate with sSFR for galaxies with the R1213 measurement. Our results support the scenario where R1213 variation is mainly caused by changes in molecular gas properties such as temperature and turbulence. The consequent variation of the CO-to-H2 conversion factor across the SF main sequence is not large enough to completely extinguish the known correlations between sSFR and Mmol/Mstar (μmol) or star-formation efficiency (SFE) reported in previous studies, while this variation would strengthen (weaken) the sSFR–SFE (sSFR–μmol) correlation.
  • Muraoka, Kazuyuki, Sorai, Kazuo, Miyamoto, Yusuke, Yoda, Moe, Morokuma-Matsui, Kana, Kobayashi, Masato I. N., Kuroda, Mayu, Kaneko, Hiroyuki, Kuno, Nario, Takeuchi, Tsutomu T., Nakanishi, Hiroyuki, Watanabe, Yoshimasa, Tanaka, Takahiro, Yasuda, Atsushi, Yajima, Yoshiyuki, Shibata, Shugo, Salak, Dragan, Espada, Daniel, Matsumoto, Naoko, Noma, Yuto, Kita, Shoichiro, Komatsuzaki, Ryusei, Kajikawa, Ayumi, Yashima, Yu, Pan, Hsi-An, Oi, Nagisa, Seta, Masumichi, Nakai, Naomasa
    Publications of the Astronomical Society of Japan 2019/12 
    We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, 71, S14). The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10-9 yr-1, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r25 < 0.3, where r25 is the B-band isophotal radius at 25 mag arcsec-2) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H2 conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r25 = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....
  • Yajima, Yoshiyuki, Sorai, Kazuo, Kuno, Nario, Muraoka, Kazuyuki, Miyamoto, Yusuke, Kaneko, Hiroyuki, Nakanishi, Hiroyuki, Nakai, Naomasa, Tanaka, Takahiro, Sato, Yuya, Salak, Dragan, Morokuma-Matsui, Kana, Matsumoto, Naoko, Pan, Hsi-An, Noma, Yuto, Takeuchi, Tsutomu T., Yoda, Moe, Kuroda, Mayu, Yasuda, Atsushi, Oi, Nagisa, Shibata, Shugo, Seta, Masumichi, Watanabe, Yoshimasa, Kita, Shoichiro, Komatsuzaki, Ryusei, Kajikawa, Ayumi, Yashima, Yu
    Publications of the Astronomical Society of Japan 2019/12 
    We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H2) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H2) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H2), with a correlation coefficient of ̃0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H2) increases as ∆V/sin i increases when ∆V/sin i < 100 km s-1. On the other hand, n(H2) decreases as ∆V/sin i increases when ∆V/sin i > 100 km s-1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....
  • Salak, Dragan, Noma, Yuto, Sorai, Kazuo, Miyamoto, Yusuke, Kuno, Nario, Pettitt, Alex R., Kaneko, Hiroyuki, Tanaka, Takahiro, Yasuda, Atsushi, Kita, Shoichiro, Yajima, Yoshiyuki, Shibata, Shugo, Nakai, Naomasa, Seta, Masumichi, Muraoka, Kazuyuki, Kuroda, Mayu, Nakanishi, Hiroyuki, Takeuchi, Tsutomu T., Yoda, Moe, Morokuma-Matsui, Kana, Watanabe, Yoshimasa, Matsumoto, Naoko, Oi, Nagisa, Pan, Hsi-An, Kajikawa, Ayumi, Yashima, Yu, Komatsuzaki, Ryusei
    Publications of the Astronomical Society of Japan 2019/12 [Refereed][Not invited]
     
    The 12CO (J = 1→0) velocity fields of a sample of 20 nearby spiral galaxies, selected from the CO Multi-line Imaging of Nearby Galaxies (COMING) legacy project of Nobeyama Radio Observatory, have been analyzed by Fourier decomposition to determine their basic kinematic properties, such as circular and noncircular velocities. On average, the investigated barred (SAB and SB) galaxies exhibit a ratio of noncircular to circular velocities of molecular gas larger by a factor of 1.5-2 than non-barred (SA) spiral galaxies at radii within the bar semimajor axis ab at 1 kpc resolution, with a maximum at a radius of R/ab ≈ 0.3. Residual velocity field images, created by subtracting model velocity fields from the data, reveal that this trend is caused by kpc-scale streaming motions of molecular gas in the bar region. Applying a new method based on radial velocity reversal, we estimated the corotation radius RCR and bar pattern speed Ωb in seven SAB and SB systems. The ratio of the corotation to bar radius is found to be in a range of R≡ R_CR/a_b ≈ 0.8-1.6, suggesting that intermediate (SBb-SBc), luminous barred spiral galaxies host fast and slow rotator bars. Tentative negative correlations are found for Ωb vs. ab and Ωb vs. total stellar mass M*, indicating that bars in massive disks are larger and rotate slower, possibly a consequence of angular momentum transfer. The kinematic properties of SAB and SB galaxies, derived from Fourier decomposition, are compared with recent numerical simulations that incorporate various rotation curve models and galaxy interactions....
  • Sorai, Kazuo, Kuno, Nario, Muraoka, Kazuyuki, Miyamoto, Yusuke, Kaneko, Hiroyuki, Nakanishi, Hiroyuki, Nakai, Naomasa, Yanagitani, Kazuki, Tanaka, Takahiro, Sato, Yuya, Salak, Dragan, Umei, Michiko, Morokuma-Matsui, Kana, Matsumoto, Naoko, Ueno, Saeko, Pan, Hsi-An, Noma, Yuto, Takeuchi, Tsutomu T., Yoda, Moe, Kuroda, Mayu, Yasuda, Atsushi, Yajima, Yoshiyuki, Oi, Nagisa, Shibata, Shugo, Seta, Masumichi, Watanabe, Yoshimasa, Kita, Shoichiro, Komatsuzaki, Ryusei, Kajikawa, Ayumi, Yashima, Yu, Cooray, Suchetha, Baji, Hiroyuki, Segawa, Yoko, Tashiro, Takami, Takeda, Miho, Kishida, Nozomi, Hatakeyama, Takuya, Tomiyasu, Yuto, Saita, Chey
    Publications of the Astronomical Society of Japan 2019/12 [Refereed][Not invited]
     
    Observations of the molecular gas in galaxies are vital to understand the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs at sufficient resolution to distinguish galactic structures are severely lacking. Millimeter-wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared (FIR) flux in 12CO, 13CO, and C18O J = 1-0 lines. The total molecular gas mass was derived using the standard CO-to-H2 conversion factor and found to be positively correlated with the total stellar mass derived from the WISE 3.4 μm band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, or the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies....
  • Yajima, Yoshiyuki, Sorai, Kazuo, Kuno, Nario, Muraoka, Kazuyuki, Miyamoto, Yusuke, Kaneko, Hiroyuki, Nakanishi, Hiroyuki, Nakai, Naomasa, Tanaka, Takahiro, Sato, Yuya, Salak, Dragan, Morokuma-Matsui, Kana, Matsumoto, Naoko, Pan, Hsi-An, Noma, Yuto, Takeuchi, Tsutomu T., Yoda, Moe, Kuroda, Mayu, Yasuda, Atsushi, Oi, Nagisa, Shibata, Shugo, Seta, Masumichi, Watanabe, Yoshimasa, Kita, Shoichiro, Komatsuzaki, Ryusei, Kajikawa, Ayumi, Yashima, Yu
    Publications of the Astronomical Society of Japan 2019/12 [Refereed][Not invited]
     
    We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H2) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H2) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H2), with a correlation coefficient of ̃0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H2) increases as ∆V/sin i increases when ∆V/sin i < 100 km s-1. On the other hand, n(H2) decreases as ∆V/sin i increases when ∆V/sin i > 100 km s-1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....
  • Muraoka, Kazuyuki, Sorai, Kazuo, Miyamoto, Yusuke, Yoda, Moe, Morokuma-Matsui, Kana, Kobayashi, Masato I. N., Kuroda, Mayu, Kaneko, Hiroyuki, Kuno, Nario, Takeuchi, Tsutomu T., Nakanishi, Hiroyuki, Watanabe, Yoshimasa, Tanaka, Takahiro, Yasuda, Atsushi, Yajima, Yoshiyuki, Shibata, Shugo, Salak, Dragan, Espada, Daniel, Matsumoto, Naoko, Noma, Yuto, Kita, Shoichiro, Komatsuzaki, Ryusei, Kajikawa, Ayumi, Yashima, Yu, Pan, Hsi-An, Oi, Nagisa, Seta, Masumichi, Nakai, Naomasa
    Publications of the Astronomical Society of Japan 2019/12 [Refereed][Not invited]
     
    We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, 71, S14). The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10-9 yr-1, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r25 < 0.3, where r25 is the B-band isophotal radius at 25 mag arcsec-2) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H2 conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r25 = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....
  • Nagoshi, Halca, Kubose, Yuzo, Fujisawa, Kenta, Sorai, Kazuo, Yonekura, Yoshinori, Sugiyama, Koichiro, Niinuma, Kotaro, Motogi, Kazuhito, Aoki, Takahiro
    Publications of the Astronomical Society of Japan 71 80  2019/08 [Refereed][Not invited]
  • Watanabe, Yoshimasa, Nishimura, Yuri, Sorai, Kazuo, Sakai, Nami, Kuno, Nario, Yamamoto, Satoshi
    The Astrophysical Journal Supplement Series 242 26  2019/06 [Refereed][Not invited]
  • Yoshiyuki Yajima, Kazuo Sorai, Nario Kuno, Kazuyuki Muraoka, Yusuke Miyamoto, Hiroyuki Kaneko, Hiroyuki Nakanishi, Naomasa Nakai, Takahiro Tanaka, Yuya Sato, Dragan Salak, Kana Morokuma-Matsui, Naoko Matsumoto, Hsi-An Pan, Yuto Noma, Tsutomu T Takeuchi, Moe Yoda, Mayu Kuroda, Atsushi Yasuda, Nagisa Oi, Shugo Shibata, Masumichi Seta, Yoshimasa Watanabe, Shoichiro Kita, Ryusei Komatsuzaki, Ayumi Kajikawa, Yu Yashima
    Publications of the Astronomical Society of Japan 71 (Supplement_1) 0004-6264 2019/03 [Refereed][Not invited]
     
    We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H<SUB>2</SUB>) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R<SUB>12/13</SUB>) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R<SUB>12/13</SUB> via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H<SUB>2</SUB>) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H<SUB>2</SUB>), with a correlation coefficient of ̃0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H<SUB>2</SUB>) increases as ∆V/sin i increases when ∆V/sin i &lt; 100 km s<SUP>-1</SUP>. On the other hand, n(H<SUB>2</SUB>) decreases as ∆V/sin i increases when ∆V/sin i &gt; 100 km s<SUP>-1</SUP>. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....
  • Kazuyuki Muraoka, Kazuo Sorai, Yusuke Miyamoto, Moe Yoda, Kana Morokuma-Matsui, Masato I N Kobayashi, Mayu Kuroda, Hiroyuki Kaneko, Nario Kuno, Tsutomu T Takeuchi, Hiroyuki Nakanishi, Yoshimasa Watanabe, Takahiro Tanaka, Atsushi Yasuda, Yoshiyuki Yajima, Shugo Shibata, Dragan Salak, Daniel Espada, Naoko Matsumoto, Yuto Noma, Shoichiro Kita, Ryusei Komatsuzaki, Ayumi Kajikawa, Yu Yashima, Hsi-An Pan, Nagisa Oi, Masumichi Seta, Naomasa Nakai
    Publications of the Astronomical Society of Japan 71 (Supplement_1) 0004-6264 2019/03 [Refereed][Not invited]
     
    We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, submitted).The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10<SUP>-9</SUP> yr<SUP>-1</SUP>, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r<SUB>25</SUB> &lt; 0.3, where r<SUB>25</SUB> is the B-band isophotal radius at 25 mag arcsec<SUP>-2</SUP>) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H<SUB>2</SUB> conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r<SUB>25</SUB> = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....
  • Ryo Ando, Kotaro Kohno, Hideki Umehata, Takuma Izumi, Shun Ishii, Yuri Nishimura, Kazuo Sorai, Tomoka Tosaki, Akio Taniguchi, Yoichi Tamura
    The Astrophysical Journal 2019/02/05 [Refereed][Not invited]
  • Dragan Salak, Yuto Noma, Kazuo Sorai, Yusuke Miyamoto, Nario Kuno, Alex R Pettitt, Hiroyuki Kaneko, Takahiro Tanaka, Atsushi Yasuda, Shoichiro Kita, Yoshiyuki Yajima, Shugo Shibata, Naomasa Nakai, Masumichi Seta, Kazuyuki Muraoka, Mayu Kuroda, Hiroyuki Nakanishi, Tsutomu T Takeuchi, Moe Yoda, Kana Morokuma-Matsui, Yoshimasa Watanabe, Naoko Matsumoto, Nagisa Oi, Hsi-An Pan, Ayumi Kajikawa, Yu Yashima, Ryusei Komatsuzaki
    Publications of the Astronomical Society of Japan 0004-6264 2019/02 [Refereed][Not invited]
     
    The <SUP>12</SUP>CO (J = 1→0) velocity fields of a sample of 20 nearby spiral galaxies, selected from the CO Multi-line Imaging of Nearby Galaxies (COMING) legacy project of Nobeyama Radio Observatory, have been analyzed by Fourier decomposition to determine their basic kinematic properties, such as circular and noncircular velocities. On average, the investigated barred (SAB and SB) galaxies exhibit a ratio of noncircular to circular velocities of molecular gas larger by a factor of 1.5-2 than non-barred (SA) spiral galaxies at radii within the bar semimajor axis a<SUB>b</SUB> at 1 kpc resolution, with a maximum at a radius of R/a<SUB>b</SUB> ≈ 0.3. Residual velocity field images, created by subtracting model velocity fields from the data, reveal that this trend is caused by kpc-scale streaming motions of molecular gas in the bar region. Applying a new method based on radial velocity reversal, we estimated the corotation radius R<SUB>CR</SUB> and bar pattern speed Ω<SUB>b</SUB> in seven SAB and SB systems. The ratio of the corotation to bar radius is found to be in a range of R≡ R_CR/a_b ≈ 0.8-1.6, suggesting that intermediate (SBb-SBc), luminous barred spiral galaxies host fast and slow rotator bars. Tentative negative correlations are found for Ω<SUB>b</SUB> vs. a<SUB>b</SUB> and Ω<SUB>b</SUB> vs. total stellar mass M<SUB>*</SUB>, indicating that bars in massive disks are larger and rotate slower, possibly a consequence of angular momentum transfer. The kinematic properties of SAB and SB galaxies, derived from Fourier decomposition, are compared with recent numerical simulations that incorporate various rotation curve models and galaxy interactions....
  • Tatsuya Takekoshi, Tetsuhiro Minamidani, Shinya Komugi, Kotaro Kohno, Tomoka Tosaki, Kazuo Sorai, Erik Muller, Norikazu Mizuno, Akiko Kawamura, Toshikazu Onishi, Yasuo Fukui, Caroline Bot, Monica Rubio, Hajime Ezawa, Tai Oshima, Jason E. Austermann, Hiroshi Matsuo, Itziar Aretxaga, David H. Hughes, Ryohei Kawabe, Grant W. Wilson, Min S. Yun
    The Astrophysical Journal 867 (2) 117 - 117 1538-4357 2018/11/06 [Refereed]
     
    We present a high-sensitivity (1 sigma < 1.6 mJy beam(-1)) continuum observation in a 343 arcmin(2) area of the northeast region of the Small Magellanic Cloud at a wavelength of 1.1. mm, conducted using the AzTEC instrument on the ASTE telescope. In the observed region, we identified 20 objects by contouring 10 sigma emission. Through spectral energy distribution analysis using 1.1 mm, Herschel, and Spitzer data, we estimated gas masses of 5 x 10(3)-7 x 10(4) M-circle dot, assuming a gas-to-dust ratio of 1000. The dust temperature and index of emissivity were also estimated as 18-33 K and 0.9-1.9, respectively, which are consistent with previous low-resolution studies. The dust temperature and the index of emissivity shows a weak negative linear correlation. We also investigated five CO-detected, dust-selected clouds in detail. The total gas masses were comparable to those estimated from the Mopra CO data, indicating that the assumed gas-to-dust ratio of 1000 and the X-CO factor of 1 x 10(21) cm(-2) (Kkms(-1))(-1), with uncertainties of a factor of 2, are reliable for the estimation of the gas masses of molecular or dust-selected clouds. The dust column density showed good spatial correlation with CO emission, except for an object associated with bright young stellar objects. The 8 mu m filamentary and clumpy structures also showed a spatial distribution similar to that of the CO emission and dust column density, supporting the fact that polycyclic aromatic hydrocarbon emissions arise from the surfaces of dense gas and dust clouds.
  • Takekoshi, T, Minamidani, T, Komugi, S, Kohno, K, Tosaki, T, Sorai, K, Muller, E, Mizuno, N, Kawamura, A, Onishi, T, Fukui, Y, Bot, C, Rubio, M, Ezawa, H, Oshima, T, Austermann, J. E, Matsuo, H, Aretxaga, I, Hughes, D. H, Kawabe, R, WILSON, G. W, Yun, M. S
    The Astrophysical Journal 2017 1347-0639 2018/09 [Refereed][Not invited]
  • VERA monitoring of the radio jet 3C 84 during 2007--2013: in the period of non-linear motion
    Hiura, K, Nagai, H, Kino, M, Niinuma, K, Sorai, K, Chida, H, Akiyama, K, D’Ammando, F, Giovannini, G, Giroletti, M, Hada, K, Honma, M, Koyama, S, Orienti, M, Orosz, G, Sawada-Satoh, S
    Publications of the Astronomical Society of Japan 2018/07 [Refereed][Not invited]
  • Ryo Ando, Kouichiro Nakanishi, Kotaro Kohno, Takuma Izumi, Sergio Martín, Nanase Harada, Shuro Takano, Nario Kuno, Naomasa Nakai, Hajime Sugai, Kazuo Sorai, Tomoka Tosaki, Kazuya Matsubayashi, Taku Nakajima, Yuri Nishimura, Yoichi Tamura
    The Astrophysical Journal 849 (2) 81 - 81 2017/11/06 [Refereed][Not invited]
  • A Face-on Accretion System in High-mass Star Formation: Possible Dusty Infall Streams within 100 AU
    Motogi, K, Hirota, T, Sorai, K, Yonekura, Y, Sugiyama, K, Honma, M, Niinuma, K, Hachisuka, K, Fujisawa, K, Walsh, A. J
    The Astrophysical Journal, 849 (1) 23:1 - 23:13 2017/11 [Refereed][Not invited]
  • Tomoki Morokuma, Masaomi Tanaka, Yasuyuki T. Tanaka, Ryosuke Itoh, Nozomu Tominaga, Poshak Gandhi, Elena Pian, Paolo Mazzali, Kouji Ohta, Emiko Matsumoto, Takumi Shibata, Hinako Akimoto, Hiroshi Akitaya, Gamal B. Ali, Tsutomu Aoki, Mamoru Doi, Nana Ebisuda, Ahmed Essam, Kenta Fujisawa, Hideo Fukushima, Shuhei Goda, Yuya Gouda, Hidekazu Hanayama, Yasuhito Hashiba, Osamu Hashimoto, Kenzo Hayashida, Yuichiro Hiratsuka, Satoshi Honda, Masataka Imai, Kanichiro Inoue, Michiko Ishibashi, Ikuru Iwata, Hideyuki Izumiura, Yuka Kanda, Miho Kawabata, Kenji Kawaguchi, Nobuyuki Kawai, Mitsuru Kokubo, Daisuke Kuroda, Hiroyuki Maehara, Hiroyuki Mito, Kazuma Mitsuda, Ryota Miyagawa, Takeshi Miyaji, Yusuke Miyamoto, Kumiko Morihana, Yuki Moritani, Kana Morokuma-Matsui, Kotone Murakami, Katsuhiro L. Murata, Takahiro Nagayama, Kazuki Nakamura, Tatsuya Nakaoka, Kotaro Niinuma, Takafumi Nishimori, Daisaku Nogami, Yumiko Oasa, Tatsunori Oda, Tomohito Ohshima, Yoshihiko Saito, Shuichiro Sakata, Shigeyuki Sako, Yuki Sarugaku, Satoko Sawada-Satoh, Genta Seino, Kazuo Sorai, Takao Soyano, Francesco Taddia, Jun Takahashi, Yuhei Takagi, Katsutoshi Takaki, Koji Takata, Ken'ichi Tarusawa, Makoto Uemura, Takahiro Ui, Riku Urago, Kazutoshi Ushioda, Jun-ichi Watanabe, Makoto Watanabe, Satoshi Yamashita, Kenshi Yanagisawa, Yoshinori Yonekura, Michitoshi Yoshida
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 69 (5) 82:1 - 82:20 0004-6264 2017/10 [Refereed][Not invited]
     
    We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSSJ110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to similar to 5 mu m in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of alpha(upsilon) similar to -1.4, where f(v) proportional to v(alpha upsilon), synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seemsmost plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low.peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.
  • Takuya Hatakeyama, Nario Kuno, Kazuo Sorai, Hiroyuki Kaneko, Yusuke Miyamoto, Kazuyuki Muraoka, Miho Takeda, Kazuki Yanagitani, Nozomi Kishida, Michiko Umei, Takahiro Tanaka, Yuto Tomiyasu, Hiroyuki Nakanishi, Chey Saita, Saeko Ueno, Dragan Salak, Naoko Matsumoto, Kana Morokuma-Matsui, Hsi-An Pan, Naomasa Nakai
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 69 (4) 67:1 - 67:14 0004-6264 2017/08 [Refereed][Not invited]
     
    In this study, we present the results of (CO)-C-12(J = 1-0), (CO)-C-13(J = 1-0), and (CO)-O-18(J = 1-0) simultaneous observations of the dwarf galaxy NGC2976 conducted as a part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project using the Nobeyama 45 m telescope. We investigated the properties of the molecular gas and star formation in NGC2976. We found that the molecular gas fraction depends on the surface densities of the total gas and the star formation rate, according to the main stellar disks of spiral galaxies. The ratio of (CO)-C-12(J = 3-2) to (CO)-C-12(J = 1-0) implies that the temperature of the molecular gas increases with decreases in the surface density of molecular gas. We detected (CO)-C-13(J = 1-0) by using the stacking method. The ratio between the integrated intensities of (CO)-C-12(J = 1-0) and (CO)-C-13(J = 1-0) was 27 +/- 11. These ratios imply that the diffuse gas phase is dominant in low surface density regimes. We obtained a lower limit of the ratio between the integrated intensities of (CO)-C-12(J = 1-0) and (CO)-O-18(J = 1-0) of 21. The relation between the surface densities of the total gas and the star formation rate followed a power-law index of 2.08 +/- 0.11, which was larger than that between the surface densities of the molecular gas and the star formation rate (1.62 +/- 0.17). The steep slope in the relation between the surface densities of the total gas and the star formation rate can be attributed to the rapid increase in the fraction of molecular gas at the surface density of similar to 10M(circle dot). The kinematics of the molecular gas suggest that the bar-like feature rotates with a rigid-body rotation curve rather than a certain pattern speed.
  • Kazuhito Motogi, Tomoya Hirota, Kazuo Sorai, Yoshinori Yonekura, Koichiro Sugiyama, Mareki Honma, Kotaro Niinuma, Kazuya Hachisuka, Kenta Fujisawa, Andrew J. Walsh
    Proceedings of the International Astronomical Union 13 (336) 267 - 270 1743-9221 2017 
    We report on interferometric observations of a face-on accretion system around the high mass young stellar object, G353.273+0.641. The innermost accretion system of 100-au radius was resolved in a 45-GHz continuum image taken with the Jansky Very Large Array. Our SED analysis indicated that the continuum could be explained by optically-thick dust emission. 6.7 GHz CH3OH masers associated with the same system were also observed with the Australia Telescope Compact Array. The masers showed a spiral-like, non-axisymmetric distribution with a systematic velocity gradient. The line-of-sight velocity field is explained by an infall motion along a parabolic streamline that falls onto the equatorial plane of the face-on system. The streamline is quasi-radial and reaches the equatorial plane at a radius of 16 au. The physical origin of such a streamline is still an open question and will be constrained by the higher-resolution thermal continuum and line observations with ALMA long baselines.
  • Tatsuya Takekoshi, Tetsuhiro Minamidani, Shinya Komugi, Kotaro Kohno, Tomoka Tosaki, Kazuo Sorai, Erik Muller, Norikazu Mizuno, Akiko Kawamura, Toshikazu Onishi, Yasuo Fukui, Hajime Ezawa, Tai Oshima, Kimberly S. Scott, Jason E. Austermann, Hiroshi Matsuo, Itziar Aretxaga, David H. Hughes, Ryohei Kawabe, Grant W. Wilson, Min S. Yun
    ASTROPHYSICAL JOURNAL 835 (1) 55:1 - 55:17 0004-637X 2017/01 [Refereed][Not invited]
     
    The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg(2) of the SMC with 1 sigma noise levels of 5-12 mJy beam(-1), and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 mu m, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500 mu m). The 1.1 mm objects show dust temperatures of 17-45 K and gas masses of 4 x 10(3)-3 x 10(5) M-circle dot, assuming single-temperature thermal emission from the cold dust with an emissivity index, beta, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 mu m and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 mu m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.
  • Kazuhito Motogi, Kazuo Sorai, Mareki Honma, Tomoya Hirota, Kazuya Hachisuka, Kotaro Niinuma, Koichiro Sugiyama, Yoshinori Yonekura, Kenta Fujisawa
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 (5) 69:1 - 69:17 0004-6264 2016/10 [Refereed][Not invited]
     
    We report on long-term single-dish and VLBI monitoring for intermittent flare activities of a dominant blue-shifted H2O maser associated with a southern high mass young stellar object, G353.273+0.641. Bi-weekly single-dish monitoring using the Hokkaido University Tomakomai 11 m radio telescope has shown that a systematic acceleration continues over four years beyond the lifetime of individual maser features. This fact suggests that the H2O maser traces a region where molecular gas is steadily accelerated. There were five maser flares during the five years of monitoring, and maser distributions in four of them were densely monitored by VLBI Exploration of Radio Astrometry (VERA). The overall distribution of the maser features suggests the presence of a bipolar jet, with the 3D kinematics indicating that it is almost face-on (inclination angle of similar to 8 degrees-17 degrees from the line of sight). Most maser features were recurrently excited within a region of 100x100 au(2) around the radio continuum peak, while their spatial distributions significantly varied between each flare. This confirms that episodic propagations of outflow shocks recurrently invoke intermittent flare activities. We also measured annual parallax, deriving a source distance of 1.70(-0.16)(+0.19) kpc that is consistent with the commonly used photometric distance.
  • Koichiro Sugiyama, Kenta Fujisawa, Kazuya Hachisuka, Yoshinori Yonekura, Kazuhito Motogi, Satoko Sawada-Satoh, Naoko Matsumoto, Daiki Hirano, Kyonosuke Hayashi, Hideyuki Kobayashi, Noriyuki Kawaguchi, Katsunori M. Shibata, Mareki Honma, Tomoya Hirota, Yasuhiro Murata, Akihiro Doi, Hideo Ogawa, Kimihiro Kimura, Kotaro Niinuma, Xi Chen, Bo Xia, Bin Li, Kazuo Sorai, Munetake Momose, Yu Saito, Hiroshi Takaba, Toshihiro Omodaka, Kee-Tae Kim, Zhiqiang Shen
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 (5) 72:1 - 72:18 0004-6264 2016/10 [Refereed][Not invited]
     
    We detected internal proper motions of the methanol maser features at 6.7 GHz in a high-mass star-forming region G006.79-00.25 with the East-Asian VLBI Network. The spatial distribution of the maser features shows an elliptical morphology. The internal proper motions of 17 methanol maser features relative to the barycenter of the features were measured. The amplitude of the internal motions ranged from 1.30 to 10.25 kms(-1). Most of the internal proper motions of the maser features seem to point counter-clockwise along the elliptical morphology of the maser features. We applied the disk model, which includes both rotating and expanding components, to the observed positions, i.o.s. velocities, and proper motions. The derived rotation, expansion, and systemic velocities are +3(-2)(+2), +6(-2)(+2), and +21(-2)(+2) kms(-1), respectively, at the radius of 1260 au on the disk with a position angle of the semi-major axis of -140 degrees. and an inclination of 60 degrees. The derived rotating motion suggests that the methanol maser emissions showing the elliptical spatial morphology possibly trace the rotating disk. The derived expanding motion might be caused by the magnetic-centrifugal wind on the disk, which was estimated on the basis of the typical magnetic field strength at emitting zones of a methanol maser.
  • Yoshinori Yonekura, Yu Saito, Koichiro Sugiyama, Kang Lou Soon, Munetake Momose, Masayoshi Yokosawa, Hideo Ogawa, Kimihiro Kimura, Yasuhiro Abe, Atsushi Nishimura, Yutaka Hasegawa, Kenta Fujisawa, Tomoaki Ohyama, Yusuke Kono, Yusuke Miyamoto, Satoko Sawada-Satoh, Hideyuki Kobayashi, Noriyuki Kawaguchi, Mareki Honma, Katsunori M. Shibata, Katsuhisa Sato, Yuji Ueno, Takaaki Jike, Yoshiaki Tamura, Tomoya Hirota, Atsushi Miyazaki, Kotaro Niinuma, Kazuo Sorai, Hiroshi Takaba, Kazuya Hachisuka, Tetsuro Kondo, Mamoru Sekido, Yasuhiro Murata, Naomasa Nakai, Toshihiro Omodaka
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 (5) 74:1 - 74:16 0004-6264 2016/10 [Refereed][Not invited]
     
    The Hitachi and Takahagi 32 m radio telescopes (former satellite communication antennas) were so upgraded as to work at 6, 8, and 22 GHz. We developed the receiver systems, IF systems, back-end systems (including samplers and recorders), and reference systems. We measured the performance of the antennas. The system temperature including the atmosphere toward the zenith, T*(sys), is measured to be similar to 30-40 K for 6 GHz and similar to 25-35 K for 8 GHz. T*(sys) for 22 GHz is measured to be similar to 40-100 K in winter and similar to 150-500K in summer seasons, respectively. The aperture efficiency is 55%-75% for Hitachi at 6 GHz and 8 GHz, and 55%-65% for Takahagi at 8 GHz. The beam sizes at 6 GHz and 8 GHz are similar to 4.'6 and similar to 3.'8, respectively. The side-lobe level is less than 3%-4% at 6 and 8 GHz. Pointing accuracy was measured to be better than similar to 0.'3 for Hitachi and similar to 0.'6 for Takahagi. We succeeded in VLBI observations in 2010 August, indicating good performance of the antenna. We started single-dish monitoring observations of 6.7 GHz methanol maser sources in 2012 December, and found several new sources showing short-term periodic variation of the flux density.
  • Kazuyuki Muraoka, Kazuo Sorai, Nario Kuno, Naomasa Nakai, Hiroyuki Nakanishi, Miho Takeda, Kazuki Yanagitani, Hiroyuki Kaneko, Yusuke Miyamoto, Nozomi Kishida, Takuya Hatakeyama, Michiko Umei, Takahiro Tanaka, Yuto Tomiyasu, Chey Saita, Saeko Ueno, Naoko Matsumoto, Dragan Salak, Kana Morokuma-Matsui
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 (5) 89:1 - 89:14 0004-6264 2016/10 [Refereed][Not invited]
     
    We present simultaneous mappings of J = 1-0 emission of (CO)-C-12, (CO)-C-13, and (CO)-O-18 molecules toward the whole disk (8' x 5' or 20.8 kpc x 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45m telescope at an effective angular resolution of 20 '' (or 870 pc). We detected (CO)-C-12(J = 1-0)emission over the disk of NGC 2903. In addition, significant (CO)-C-13(J = 1-0) emission was found at the center and bar-ends, whereas we could not detect any significant (CO)-O-18(J = 1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of (CO)-C-12(J = 2-1)/(CO)-C-12(J = 1-0) (R2-1/1-0) and (CO)-C-13(J = 1-0)/(CO)-C-12(J = 1-0) (R-13/12), we performed the stacking analysis for our (CO)-C-12(J = 1-0), (CO)-C-13(J = 1-0), and archival (CO)-C-12(J = 2-1) spectra with velocity axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged R2-1/1-0 and R-13/12 with high significance for all the regions. We found that both R2-1/1-0 and R-13/12 differ according to the regions, which reflects the difference in the physical properties of molecular gas, i.e., density (n(H2)) and kinetic temperature (T-K). We determined n(H2) and T-K using R2-1/1-0 and R-13/12 based on the large velocity gradient approximation. The derived n(H2) ranges from similar to 1000 cm(-3) (in the bar, bar-ends, and spiral arms) to 3700 cm(-3) (at the center) and the derived T-K ranges from 10 K (in the bar and spiral arms) to 30 K (at the center). We examined the dependence of star formation efficiencies (SFEs) on n(H2) and T-K, and found a positive correlation between SFE and n(H2) with correlation coefficient for the least-squares power-law fit R-2 of 0.50. This suggests that molecular gas density governs the spatial variations in SFEs.
  • Kazuyuki Muraoka, Miho Takeda, Kazuki Yanagitani, Hiroyuki Kaneko, Kouichiro Nakanishi, Nario Kuno, Kazuo Sorai, Tomoka Tosaki, Kotaro Kohno
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 68 (2) 18:1 - 18:13 0004-6264 2016/04 [Refereed][Not invited]
     
    We present the results of CO(J= 3-2) on-the-fly mappings of two nearby non-barred spiral galaxies, NGC628 and NGC7793, with the Atacama Submillimeter Telescope Experiment at an effective angular resolution of 25 ''. We successfully obtained global distributions of CO(J = 3-2) emission over the entire disks at a sub-kpc resolution for both galaxies. We examined the spatially resolved (sub-kpc) relationship between CO(J = 3-2) luminosities (LCO(3-2)') and infrared (IR) luminosities (L-IR) for NGC628, NGC7793, and M83, and compared it with global luminosities of a JCMT (James Clerk Maxwell Telescope) Nearby Galaxy Legacy Survey sample. We found a striking linear L'(CO(3-2))-L-IR correlation over the four orders of magnitude, and the correlation is consistent even with that for ultraluminous IR galaxies and submillimeter-selected galaxies. In addition, we examined the spatially resolved relationship between CO(J = 3-2) intensities (ICO(3-2)) and extinctioncorrected star formation rates (SFRs) for NGC628, NGC7793, and M83, and compared it with that for Giant Molecular Clouds in M33 and 14 nearby galaxy centers. We found a linear ICO(3-2)-SFR correlation with similar to 1 dex scatter. We conclude that the CO(J = 3-2) star-formation law (i. e., linear L'(CO(3-2))-L-IR and ICO(3-2)-SFR correlations) is universally applicable to various types and spatial scales of galaxies; from spatially resolved nearby galaxy disks to distant IR-luminous galaxies, within similar to 1 dex scatter.
  • Kana Morokuma-Matsui, Jin Koda, Tatsuya Takekoshi, Masao Saito, Hiroyuki Nakanishi, Samuel Boissier, Barry F. Madore, Alessandro Boselli, Armando Gil de Paz, David Thilker, Masafumi Yagi, Kazuo Sorai, Nario Kuno
    Proceedings of the International Astronomical Union 11 (S321) 268 - 268 2016/03 [Refereed][Not invited]
  • Yoshimasa Watanabe, Nami Sakai, Kazuo Sorai, Junko Ueda, Satoshi Yamamoto
    ASTROPHYSICAL JOURNAL 819 (2) 144:1 - 144:11 0004-637X 2016/03 [Refereed][Not invited]
     
    Molecular line images of (CO)-C-13, (CO)-O-18, CN, CS, CH3OH, and HNCO are obtained toward the spiral arm of M51 at a 7 '' x 6 '' resolution with the Combined Array for Research in Millimeter-wave Astronomy. Distributions of the molecules averaged over a 300 pc scale are found to be almost similar to one another and to essentially trace the spiral arm. However, the principal component analysis shows a slight difference of distributions among molecular species, particularly for CH3OH and HNCO. These two species do not correlate well with the star formation rate, implying that they are not enhanced by local star formation activities but by galactic-scale phenomena such as spiral shocks. Furthermore, the distributions of HNCO and CH3OH are found to be slightly different, and their origins deserve further investigation. The present results provide us with an important clue for. understanding the 300 pc scale chemical composition in the spiral arm and its relation to galactic-scale dynamics.
  • Tetsuhiro Minamidani, Atsushi Nishimura, Yusuke Miyamoto, Hiroyuki Kaneko, Hiroyuki Iwashita, Chieko Miyazawa, Hiroyuki Nishitani, Takuya Wada, Yasunori Fujii, Toshikazu Takahashi, Yoshizo Iizuka, Hideo Ogawa, Kimihiro Kimura, Yuto Kozuki, Yutaka Hasegawa, Mitsuhiro Matsuo, Shinji Fujita, Satoshi Ohashi, Kana Morokuma-Matsui, Jun Maekawa, Kazuyuki Muraoka, Taku Nakajima, Tomofumi Umemoto, Kazuo Sorai, Fumitaka Nakamura, Nario Kuno, Masao Saito
    MILLIMETER, SUBMILLIMETER, AND FAR-INFRARED DETECTORS AND INSTRUMENTATION FOR ASTRONOMY VIII 9914 0277-786X 2016 [Refereed][Not invited]
     
    We report the development of the new 4-beam, 2-polarization, 2-sideband, 100 GHz band SIS receiver "FOREST" (FOur beam REceiver System on the 45-m Telescope) and the results from commissioning and observations on the Nobeyama 45-m Telescope operated by Nobeyama Radio Observatory, a branch of National Astronomical Observatory of Japan. FOREST aims to add new capabilities of large-area mapping and simultaneous multi-line observation at 80 - 116 GHz band to the Nobeyama 45-m Telescope, which is one of the largest millimeter radio telescopes in the world. The configuration of the four beams is a quadrate of 2 x 2 with the separation between adjacent beams of 50". Beam size of each beam is 15" at 115 GHz. Receiver noise temperature is as low as that of ALMA Band 3 receivers, so that mapping speed is more than four times as high as that of the other 100 GHz band receivers on the 45-m Telescope. The IF bandwidth is 8 GHz (4 - 12 GHz) realizing simultaneous (CO)-C-12 (J = 1 0), (CO)-C-13 (J = 1 0), and (CO)-O-18(J = 1 - 0) observations. Cooled components inside of cryostat are modularized per beam. IF signals from the cryostat are processed by the room temperature IF system, and then passed to spectrometers. We have installed the FOREST receiver into the Nobeyama 45-m Telescope, evaluated its performance, and made large area mapping observations. These demonstrate the excellent performance of the FOREST receiver and the Nobeyama 45-m Telescope.
  • Hsi-An Pan, Nario Kuno, Jin Koda, Akihiko Hirota, Kazuo Sorai, Hiroyuki Kaneko
    ASTROPHYSICAL JOURNAL 815 (1) 59:1 - 59:14 0004-637X 2015/12 [Refereed][Not invited]
     
    In this work, we investigate the molecular gas and star-formation properties in the barred spiral galaxy NGC 6946 using multiple molecular lines and star-formation tracers. A high-resolution image (100 pc) of (CO)-C-13 (1-0) is created for the inner 2 kpc disk by the single-dish Nobeyama Radio Observatory 45 m telescope and interferometer Combined Array for Research in Millimeter-wave Astronomy, including the central region (nuclear ring and bar) and the offset ridges of the primary bar. Single-dish HCN (1-0) observations were also made to constrain the amount of dense gas. The physical properties of molecular gas are inferred from (1) the large velocity gradient calculations using our observations and archival (CO)-C-12 (1-0), (CO)-C-12(2-1) data, (2) the dense gas fraction suggested by the luminosity ratio of HCN to (CO)-C-12 (1-0), and (3) the infrared color. The results show that the molecular gas in the central region is warmer and denser than that of the offset ridges. The dense gas fraction of the central region is similar to that of luminous infrared galaxies/ultraluminous infrared galaxies, whereas the offset ridges are close to the global average of normal galaxies. The coolest and least-dense region is found in a spiral-like structure, which was misunderstood to be part of the southern primary bar in previous low-resolution observations. The star-formation efficiency (SFE) changes by about five times in the inner disk. The variation of SFE agrees with the prediction in terms of star formation regulated by the galactic bar. We find a consistency between the star-forming region and the temperature inferred by the infrared color, suggesting that the distribution of subkiloparsec-scale temperature is driven by star formation.
  • Hsi-An Pan, Nario Kuno, Kazuo Sorai, Michiko Umei
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 67 (6) 116:1 - 116:17 0004-6264 2015/12 [Refereed][Not invited]
     
    We used multi-wavelength analysis of the newly observed molecular gas [(CO)-C-12 and (CO)-C-13(1-0)] with interferometer CARMA and archival star formation tracers to constrain the interaction, merging, and star formation history of an off-center minor merger, a three-spiral barred galaxy NGC5430 and its satellite embedded in the bar. Morphology of the molecular gas in the bar of NGC5430 shows minimal signs of recent interactions with our resolution. The apparent morphological remnant of the past galaxy interaction is an asymmetric spiral arm, containing more molecular gas and exhibiting higher star formation rate (SFR) surface density than the two primary arms. Rotation curve analysis suggests that NGC5430 collided with its satellite several Gyr ago. History of star formation was constrained by using SFRs that trace different timescales (infrared, radio continuum, and Ha). The collision occurred 5-10 Myr ago, triggering a transient off-center starburst of Wolf-Rayet stars at the eastern bar end. In the past, the global SFR during the Wolf-Rayet starburst peaked at 35M(circle dot)yr(-1). At present, the merger-driven starburst is rapidly decaying and the current global SFR has decreased to the Galactic value. The SFR will continue to decay as suggested by the present amount of dense gas [traced by HCN(1-0)]. Nonetheless, the global SFR is still dominated by the Wolf-Rayet region rather than the circumnuclear region. Compared with other barred galaxies, the circumnuclear region exhibits a particularly low dense gas fraction, low star formation activity, and high concentration of gas. Physical properties of the molecular gas are inferred by using the large velocity gradient calculations. The initial mass ratio of NGC5430 to its satellite is suggested to be in an intermediate ratio range of 7: 1-20: 1.
  • Kana Morokuma-Matsui, Junichi Baba, Kazuo Sorai, Nario Kuno
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 67 (3) 36:1 - 36:13 0004-6264 2015/06 [Refereed][Not invited]
     
    We performed (CO)-C-12(J = 1-0) (hereafter, CO) observations toward 12 normal star-forming galaxies with stellar masses of M-star = 10(10.6)-10(11.3) M-circle dot at z = 0.1-0.2 with the 45 m telescope at the Nobeyama Radio Observatory. The samples were selected with D-n(4000), that is, the strength of the 4000 angstrom break, instead of the commonly used far-infrared (FIR) flux. We successfully detected the CO emissions from eight galaxies with signal-to-noise ratio larger than three, demonstrating the effectiveness of the D-n(4000)-based sample selection. For the first time, we find a tight anti-correlation between D-n(4000) and molecular gas fraction (f(mol)) using literature data of nearby galaxies in which the galaxies with more fuel for star formation have younger stellar populations. We find that our CO-detected galaxies at z similar to 0.1-0.2 also follow the same relation as nearby galaxies. This implies that the galaxies evolve along this D-n(4000)-f(mol) relation, and that D-n(4000) seems to be able to be used as a proxy for fmol, which requires many time-consuming observations. Based on the comparison with the model calculation with a population synthesis code, we find that star formation from metal enriched gas and its quenching in the early time are necessary to reproduce galaxies with large D-n(4000) and non-zero gas fraction.
  • Kana Morokuma-Matsui, Kazuo Sorai, Yoshimasa Watanabe, Nario Kuno
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 67 (1) 0004-6264 2015/02 [Refereed][Not invited]
     
    We stacked (CO)-C-12 and (CO)-C-13 spectra of NGC3627 after redefining the velocity axis of each spectrum of the mapping data so that the zero corresponds to the local mean velocity of the (CO)-C-12 spectra. The signal-to-noise ratios of the resulting spectra are improved by a factor of up to 3.2 compared to those obtained with normal stacking analysis. We successfully detect a weak (CO)-C-13 emission from the interarm region where the emission was not detected in the individual pointings. We compare the integrated intensity ratios I-12CO/I-13CO among six characteristic regions (center, bar, bar-end, offset, arm, and interarm). We find that I-12CO/I-13CO in the bar and interarm are higher than those in the other regions by a factor of similar to 2 and I-12CO/I-13CO in the center is moderately high. These high I-12CO/I-13CO ratios in the bar and center are attributed to a high intensity ratio (T12CO/T13CO), and that in the interarm is attributed to a high ratio of the full width at half maximum of spectra (FWHM12CO/FWHM13CO). The difference between FWHM12CO and FWHM13CO of the interarm indicates the existence of two components, one with a narrow line width (similar to FWHM13CO) and the other with a broad line width (similar to FWHM12CO). Additionally, the T12CO/T13CO ratio in the broad-line-width component of the interarm is higher than the other regions. The high T12CO/T13CO in the center and bar and of the broad-line-width component in the interarm suggest the existence of non-optically thick (CO)-C-12 components. We find that more than half of the (CO)-C-12 emissions of the interarm are likely to be radiated from the diffuse component. Our result suggests that the use of a universal CO-to-H-2 conversion factor might lead to an overestimation of molecular gas mass and underestimation of star-formation efficiency in the interarm by a factor of a few.
  • Kana Morokuma-Matsui, Junichi Baba, Kazuo Sorai, Nario Kuno
    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR 499 157 - 158 2015 [Refereed][Not invited]
     
    We performed (CO)-C-12(J = 1 0) (hereafter, CO) observations towards 12 normal star-forming galaxies with M-star = 10(10.6) - 10(11.3) M-circle dot at z = 0.1 - 0.2 with the 45-m telescope at the Nobeyama Radio Observatory (NRO). The samples are selected with D-n (4000) that is a measure of the 4000 Angstrom break strength, instead of commonly used far-infrared (FIR) flux. We detect the CO emissions from 8 galaxies with signal-to-noise ratio (S/N) larger than 3, demonstrating the effectiveness of the D-n (4000)-based sample selection. We find a tight anti-correlation between D-n (4000) and molecular gas fraction (f(mol)) using literature data of nearby galaxies in which the galaxies with more fuel for star formation have younger stellar populations. CO-detected galaxies at z similar to 0.1 - 0.2 also follow the same relation of nearby galaxies, implying 1) the galaxies evolve along this D-n (4000) - f(mol) relation, and 2) D-n (4000) seems to be used as a proxy for f(mol) which requires many time-consuming observations'.
  • Watanabe Yoshimasa, Sakai Nami, Sorai Kazuo, Nishimura Yuri, Yamamoto Satoshi
    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR 499 151 - 152 2015 [Refereed][Not invited]
  • Nakanishi Kouichiro, Sorai Kazuo, Nakai Naomasa, Kuno Nario, Matsubayashi Kazuya, Sugai Hajime, Takano Shuro, Kohno Kotaro, Nakajima Taku
    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR 499 117 - 120 2015 [Refereed][Not invited]
  • Kana Morokuma-Matsui, Kazuo Sorai, Yoshimasa Watanabe, Nario Kuno
    Publications of the Astronomical Society of Japan 67 (1) 2:1 - 2:17 2053-051X 2015 [Refereed][Not invited]
     
    We stacked < sup> 12< /sup> CO and < sup> 13< /sup> CO spectra of NGC3627 after redefining the velocity axis of each spectrum of the mapping data so that the zero corresponds to the local mean velocity of the < sup> 12< /sup> CO spectra. The signal-to-noise ratios of the resulting spectra are improved by a factor of up to 3.2 compared to those obtained with normal stacking analysis. We successfully detect a weak < sup> 13< /sup> CO emission from the interarm region where the emission was not detected in the individual pointings. We compare the integrated intensity ratios I< sup> 12< /sup> CO/I< sup> 13< /sup> CO among six characteristic regions (center, bar, bar-end, offset, arm, and interarm). We find that I< sup> 12< /sup> CO/I< sup> 13< /sup> CO in the bar and interarm are higher than those in the other regions by a factor of ∼2 and I< sup> 12< /sup> CO/I< sup> 13< /sup> CO in the center ismoderately high. These high I< sup> 12< /sup> CO/I< sup> 13< /sup> CO ratios in the bar and center are attributed to a high intensity ratio (T< sup> 12< /sup> CO/T< sup> 13< /sup> CO), and that in the interarm is attributed to a high ratio of the full width at half maximum of spectra (FWHM< sup> 12< /sup> CO/FWHM< sup> 13< /sup> CO). The difference between FWHM< sup> 12< /sup> CO and FWHM< sup> 13< /sup> CO of the interarm indicates the existence of two components, one with a narrow line width (∼ FWHM< sup> 13< /sup> CO) and the other with a broad line width (∼ FWHM< sup> 12< /sup> CO). Additionally, the T< sup> 12< /sup> CO/T< sup> 13< /sup> CO ratio in the broad-line-width component of the interarm is higher than the other regions. The high T< sup> 12< /sup> CO/T< sup> 13< /sup> CO in the center and bar and of the broad-line-width component in the interarm suggest the existence of non-optically thick < sup> 12< /sup> CO components. We find that more than half of the < sup> 12< /sup> CO emissions of the interarm are likely to be radiated from the diffuse component. Our result suggests that the use of a universal CO-to-H2 conversion factor might lead to an overestimation of molecular gas mass and underestimation of star-formation efficiency in the interarm by a factor of a few.
  • Kotaro Niinuma, Sang-Sung Lee, Motoki Kino, Bong Won Sohn, Kazunori Akiyama, Guang-Yao Zhao, Satoko Sawada-Satoh, Sascha Trippe, Kazuhiro Hada, Taehyun Jung, Yoshiaki Hagiwara, Richard Dodson, Shoko Koyama, Mareki Honma, Hiroshi Nagai, Aeree Chung, Akihiro Doi, Kenta Fujisawa, Myoung-Hee Han, Joeng-Sook Kim, Jeewon Lee, Jeong Ae Lee, Atsushi Miyazaki, Tomoaki Oyama, Kazuo Sorai, Kiyoaki Wajima, Jaehan Bae, Do-Young Byun, Se-Hyung Cho, Yoon Kyung Choi, Hyunsoo Chung, Moon-Hee Chung, Seog-Tae Han, Tomoya Hirota, Jung-Wook Hwang, Do-Heung Je, Takaaki Jike, Dong-Kyu Jung, Jin-Seung Jung, Ji-Hyun Kang, Jiman Kang, Yong-Woo Kang, Yukitoshi Kan-Ya, Masahiro Kanaguchi, Noriyuki Kawaguchi, Bong Gyu Kim, Hyo Ryoung Kim, Hyun-Goo Kim, Jaeheon Kim, Jongsoo Kim, Kee-Tae Kim, Mikyoung Kim, Hideyuki Kobayashi, Yusuke Kono, Tomoharu Kurayama, Changhoon Lee, Jung-Won Lee, Sang Hyun Lee, Young Chol Minh, Naoko Matsumoto, Akiharu Nakagawa, Chung Sik Oh, Se-Jin Oh, Sun-Youp Park, Duk-Gyoo Roh, Tetsuo Sasao, Katsunori M. Shibata, Min-Gyu Song, Yoshiaki Tamura, Seog-Oh Wi, Jae-Hwan Yeom, Young Joo Yun
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 66 (6) 103:1 - 103:16 0004-6264 2014/12 [Refereed][Not invited]
     
    The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23-43 GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M87. This is one of the initial results of KaVA's early operation. Our KaVA images reveal extended outflows with complex substructures such as knots and limb brightening, in agreement with previous Very Long Baseline Array (VLBA) observations. Angular resolutions are better than 1.4 and 0.8 mas at 23 and 43 GHz, respectively. KaVA achieves a high dynamic range of similar to 1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN outflows, at least comparable to the best existing radio interferometric arrays.
  • Yoshimasa Watanabe, Nami Sakai, Kazuo Sorai, Satoshi Yamamoto
    ASTROPHYSICAL JOURNAL 788 (1) 4:1 - 4:20 0004-637X 2014/06 [Refereed][Not invited]
     
    We have conducted a spectral line survey in the 3 and 2 mm bands toward two positions in a spiral arm of M51 (NGC 5194) with the Institut de Radioastronomie Millimetrique 30 m telescope. In this survey, we have identified 13 molecular species, including CN, CCH, N2H+, HNCO, and CH3OH. Furthermore, six isotopologues of the major species have been detected. On the other hand, SiO, HC3N, CH3CN, and deuterated species such as DCN and DCO+ were not detected. The deuterium fractionation ratios are evaluated to be less than 0.8% and 1.2% for DCN/HCN and DCO+/HCO+, respectively. By comparing the results of the two positions with different star formation activities, we have found that the observed chemical compositions do not strongly depend on star formation activities. They seem to reflect a chemical composition averaged over the 1 kpc scale region including many giant molecular clouds. Among the detected molecules CN, CCH, and CH3OH are found to be abundant. High abundances of CN and CCH are consistent with the above picture of a widespread distribution of molecules because they can be produced by photodissociation. On the other hand, it seems likely that CH3OH is liberated in the gas phase by shocks associated with large-scale phenomena such as cloud-cloud collisions and/or by nonthermal desorption processes such as photoevaporation due to cosmic-ray-induced UV photons. The present result demonstrates a characteristic chemical composition of a giant molecular cloud complex in the spiral arm, which can be used as a standard reference for studying chemistry in active galactic nuclei and starbursts.
  • Kenta Fujisawa, Koichiro Sugiyama, Kazuhito Motogi, Kazuya Hachisuka, Yoshinori Yonekura, Satoko Sawada-Satoh, Naoko Matsumoto, Kazuo Sorai, Munetake Momose, Yu Saito, Hiroshi Takaba, Hideo Ogawa, Kimihiro Kimura, Kotaro Niinuma, Daiki Hirano, Toshihiro Omodaka, Hideyuki Kobayashi, Noriyuki Kawaguchi, Katsunori M. Shibata, Mareki Honma, Tomoya Hirota, Yasuhiro Murata, Akihiro Doi, Nanako Mochizuki, Zhiqiang Shen, Xi Chen, Bo Xia, Bin Li, Kee-Tae Kim
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 66 (2) 31:1 - 31:29 0004-6264 2014/04 [Refereed][Not invited]
     
    Very-long-baseline interferometry (VLBI) monitoring of the 6.7 GHz methanol maser allows us to measure the internal proper motion of maser spots and therefore study the gas motion around high-mass young stellar objects. To this end, we have begun monitoring observations with the East-Asian VLBI Network. In this paper we present the results of the first epoch observation for 36 sources, including 35 VLBI images of the methanol maser. Since two independent sources were found in three images, images of 38 sources were obtained. In 34 sources, 10 or more spots were detected. The observed spatial scale of the maser distribution was from 9 to 4900 astronomical units, and the following morphological categories were observed: elliptical, arched, linear, paired, and complex. The position of the maser spot was determined with an accuracy of approximately 0.1 mas, which is sufficiently high to measure the internal proper motion from two years of monitoring observations. The VLBI observation, however, detected only approximately 20% of all maser emissions, suggesting that the remaining 80% of the total flux was spread into an undetectable extended distribution. Therefore, in addition to high-resolution observations, it is important to observe the whole structure of the maser emission including extended low-brightness structures, in order to reveal the associated site of the maser and gas motion.
  • Kana Morokuma, Junichi Baba, Kazuo Sorai, Nario Kuno
    Proceedings of the International Astronomical Union 10 332  1743-9221 2014 [Refereed][Not invited]
     
    We found stellar mass-dependent evolution of galactic molecular gas fractions (fmol = Mmol/MBlack star+Mmol, Mmol: molecular gas mass, MBlack star : stellar mass) where less massive galaxies have decreased fmol from z = 1 whereas massive galaxies have already had low fmol until z = 1. Comparison of the observed quantities (fmol, optical and near infra-red [NIR] colors, specific star formation rate [sSFR = SFR/MBlack star]) with mass evolution models suggests that less massive galaxies had high fmol at z = 1 thanks to recent gas accretion.
  • Hikaru Nakao, Makoto Watanabe, Kazuo Sorai, Mahiro Yamada, Yoichi Itoh, Shigeyuki Sako, Takashi Miyata
    GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V 9147 91473P  0277-786X 2014 [Not refereed][Not invited]
     
    We have developed a visible imager and spectrograph, Nayoro Optical Camera and Spectrograph (NaCS), installed at the f/12 Nasmyth focus of the 1.6-m Pirka telescope of the Hokkaido University in Hokkaido, Japan. The optical and mechanical design is similar to that of WFGS2 of the University of Hawaii 2.2-m telescope (UH88), however the camera is newly designed. The spectral coverage is 380-970 nm, and the field of view is 8.4 x 4.5 arcmin with a pixel scale of 0.247 arcsec pixel(-1). The SDSS (g', r', i', z') filters, Johnson (B, V) filters and a replica grism (R similar to 300 at 650 nm) are equipped. The slit width can be selected from 2, 3, and 4 arcsec. We selected a 2k x 1k fully-depleted back-illuminated Hamamatsu CCD as a detector, because it has a high quantum efficiency (>= 80 %) over optical wavelength. The Kiso Array Controller (KAC) is used as a CCD controller. The first light observation was done on November 2011. NaCS is used mainly for long-term spectroscopic monitor of active galactic nuclei. It is also used for several astronomical observations such as light-curve measurements of asteroids and search of pre-main-sequence stars and brown dwarfs by slit-less spectroscopy as a major facility instrument of the Pirka telescope. We present the design, construction, integration, and performance of this instrument.
  • New Detection of an Extremely Blue-shift Dominated Jet in G353.273+0.641: A Possible Disk-Jet System on 100 AU Scale
    Motogi, K, Fujisawa, K, Sugiyama, K, Niinuma, K, Sorai, K, Honma, M, Hirota, T, Yonekura, Y, Hachisuka, K, Walsh, A. J
    New Trends in Radio Astronomy in the ALMA Era: The 30th Anniversary of Nobeyama Radio Observatory 476 1 - 2 2013/10 [Refereed][Not invited]
  • Tatsuya Takekoshi, Yoichi Tamura, Tetsuhiro Minamidani, Kotaro Kohno, Taira Oogi, Kazuo Sorai, Asao Habe, Hajime Ezawa, Tai Oshima, Kimberly S. Scott, Jason E. Austermann, Shinya Komugi, Tomoka Tosaki, Norikazu Mizuno, Erik Muller, Akiko Kawamura, Toshikazu Onishi, Yasuo Fukui, Hiroshi Matsuo, Itziar Aretxaga, David H. Hughes, Ryohei Kawabe, Grant W. Wilson, Min S. Yun
    The Astrophysical Journal Letters 774 (2) L30:1 - L30:6 2013/08/29 [Refereed][Not invited]
     
    We report the discovery of a new ultra-bright submillimeter galaxy (SMG) behind the Small Magellanic Cloud (SMC). This SMG is detected as a 43.3+-8.4 mJy point source (MM J01071-7302, hereafter MMJ0107) in the 1.1 mm continuum survey of the SMC by AzTEC on the ASTE telescope. MMJ0107 is also detected in the radio (843 MHz), Herschel/SPIRE, Spitzer MIPS 24 {\mu}m, all IRAC bands, Wide-field Infrared Survey Explorer, and near-infrared (J, H, KS). We find an optical (U, B, V) source, which might be the lensing object, at a distance of 1.4 arcsec from near-infrared and IRAC sources. Photometric redshift estimates for the SMG using representative spectral energy distribution templates show the redshifts of 1.4-3.9. We estimate total far-infrared luminosity of (0.3-2.2)x10^14 {\mu}^-1 L_sun and a star formation rate of 5600-39, 000 {\mu}^-1 M_sun yr^-1, where {\mu} is the gravitational magnification factor. This apparent extreme star formation activity is likely explained by a highly magnified gravitational lens system.
  • Hiroshi Nagai, Motoki Kino, Kotaro Niinuma, Kazunori Akiyama, Kazuhiro Hada, Shoko Koyama, Monica Orienti, Koichiro Hiura, Satoko Sawada-Satoh, Mareki Honma, Gabriele Giovannini, Marcello Giroletti, Katsunori Shibata, Kazuo Sorai
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 65 (2) 24:1 - 24:14 0004-6264 2013/04 [Refereed][Not invited]
     
    We introduce the gamma-ray emitting notable active galactic nucleus (AGN) monitoring by Japanese VLBI programme, which is the monitoring of gamma-ray bright AGNs with the VLBI Exploration of Radio Astrometry (VERA) array. This programme aims to conduct dense monitoring at 22 GHz toward the gamma-ray emitting AGNs to investigate the time variation of the radio core and possible ejection of a new radio component, the motion of jets, and their relations with the emission at other wavelengths, especially at gamma-rays. We are currently monitoring 8 notable gamma-ray-emitting AGNs (DA 55, 3C 84, M 87, PKS 1510-089, DA 406, NRAO 530, BL Lac, and 3C 454.3) about once every two weeks. This programme is promising for tracing the trend of radio time variation on shorter time scale than conventional VLBI monitoring programmes and is complementary to data of other programmes (e.g., MOJAVE; Boston University Blazar Project). In particular, we successfully carried out quick follow-up observations after the GeV gamma-ray flare in NRAO 530 and 3C 454.3 reported by the Fermi Gamma-ray Space Telescope. Here, we present the initial results of morphology and light curves for the first 7-month operation.
  • Akihiro Doi, Kotaro Kohno, Kouichiro Nakanishi, Seiji Kameno, Makoto Inoue, Kazuhiro Hada, Kazuo Sorai
    Astrophysical Journal 765 (1) 63:1 - 63:11 1538-4357 2013/03/01 [Refereed][Not invited]
     
    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz (α ∼ 0.3 F ν∝να) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds (Γ ≳ 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe. © 2013. The American Astronomical Society. All rights reserved.
  • M. Nimori, A. Habe, K. Sorai, Y. Watanabe, A. Hirota, D. Namekata
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 429 (3) 2175 - 2182 0035-8711 2013/03 [Refereed][Not invited]
     
    We investigate the properties of massive, dense clouds formed in a barred galaxy and their possible relation to star formation, performing a two-dimensional hydrodynamical simulation with the gravitational potential obtained from the 2MASS data from the barred spiral galaxy, M83. Since the environment for cloud formation and evolution in the bar region is expected to be different from that in the spiral arm region, barred galaxies are a good target to study the environmental effects on cloud formation and the subsequent star formation. Our simulation uses for an initial 80 Myr isothermal flow of non-self gravitating gas in the barred potential, then including radiative cooling, heating and self-gravitation of the gas for the next 40 Myr, during which dense clumps are formed. We identify many cold, dense gas clumps for which the mass is more than 10(4) M-circle dot (a value corresponding to the molecular clouds) and study the physical properties of these clumps. The relation of the velocity dispersion of the identified clump's internal motion with the clump size is similar to that observed in the molecular clouds of our Galaxy. We find that the virial parameters for clumps in the bar region are larger than that in the spiral arm region. From our numerical results, we estimate star formation in the bar and spiral arm regions by applying the simple model of Krumholz & McKee (2005). The mean relation between star formation rate and gas surface density agrees well with the observed Kennicutt-Schmidt relation. The star formation efficiency in the bar region is similar to 60 per cent of the spiral arm region. This trend is consistent with observations of barred galaxies.
  • Y. Yonekura, Y. Saito, T. Saito, T. Mori, K. L. Soon, M. Momose, M. Yokosawa, H. Ogawa, K. Fujisawa, K. Sugiyama, K. Motogi, H. Takaba, K. Sorai, N. Nakai, S. Kameno, H. Kobayashi, N. Kawaguchi, K. Hachisuka
    NEW TRENDS IN RADIO ASTRONOMY IN THE ALMA ERA: THE 30TH ANNIVERSARY OF NOBEYAMA RADIO OBSERVATORY 476 415 - 416 2013 [Refereed][Not invited]
     
    We report the renovation of two satellite-communication antennas, named Takahagi and Hitachi 32-m antennas, into cm-wave radio telescopes. Both antennas have been successfully renovated into radio telescopes until 2012. VLBI observations at 6.7, 8, and 22 GHz have been successful since 2010. We have started single-dish observations of methanol masers at 6.7 GHz and H2O masers at 22 GHz from 2013.
  • Kana Matsui, Kazuo Sorai, Junichi Baba, Yoshimasa Watanabe, Nario Kuno
    NEW TRENDS IN RADIO ASTRONOMY IN THE ALMA ERA: THE 30TH ANNIVERSARY OF NOBEYAMA RADIO OBSERVATORY 476 277 - 278 2013 [Refereed][Not invited]
     
    We observed nine barred spiral galaxies at z similar to 0.1 - 0.2 in CO(J = 1 - 0) with the 45-m telescope at the Nobeyama Radio Observatory in 2010-2011 and successfully detected emissions from seven galaxies including tentative detections. The molecular gas fraction of our samples are systematically higher than the ones of local barred galaxies as well as the expected upper-limit where the bars can be formed or survive in numerical simulations. This implies that the simulations of bar formation and evolution may need a little corrections and the formation and evolution of bars must be considered in the context of the galactic disk evolution and formation, i.e., bar formation in gas-rich disks.
  • K. Motogi, K. Sorai, K. Niinuma, K. Sugiyama, M. Honma, K. Fujisawa
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 428 (1) 349 - 353 0035-8711 2013/01 [Refereed][Not invited]
     
    We report the first detection of a radio continuum and molecular jet associated with a dominant blue-shifted maser source, G353.273+0.641. A radio jet is extended 3000 au along the north-west-south-east (NW-SE) direction. H2O masers are found to be clustered in the root of a bipolar radio jet. A molecular jet is detected by thermal SiO (upsilon = 0, J = 2-1) emission. The SiO spectrum is extremely wide (-120 to +87 km s(-1)) and significantly blue-shift dominated, similar to the maser emission. The observed geometry and remarkable spectral similarity between H2O maser and SiO strongly suggest the existence of a maser-scale (similar to 340 au) molecular jet that is enclosed by the extended radio jet. We propose a disc-masking scenario as the origin of the strong blue-shift dominance, where an optically thick disc obscures a red-shifted lobe of a compact jet.
  • Jin Koda, Nick Scoville, Tetsuo Hasegawa, Daniela Calzetti, Jennifer Donovan Meyer, Fumi Egusa, Robert Kennicutt, Nario Kuno, Melissa Louie, Rieko Momose, Tsuyoshi Sawada, Kazuo Sorai, Michiko Umei
    ASTROPHYSICAL JOURNAL 761 (1) 0004-637X 2012/12 [Refereed][Not invited]
     
    We report systematic variations in the emission line ratio of the CO J = 2-1 and J = 1-0 transitions (R2-1/1-0) in the grand-design spiral galaxy M51. The R2-1/1-0 ratio shows clear evidence for the evolution of molecular gas from the upstream interarm regions into the spiral arms and back into the downstream interarm regions. In the interarm regions, R2-1/1-0 is typically <0.7 (and often 0.4-0.6); this is similar to the ratios observed in Galactic giant molecular clouds (GMCs) with low far-infrared luminosities. However, the ratio rises to >0.7 (often 0.8-1.0) in the spiral arms, particularly at the leading (downstream) edge of the molecular arms. These trends are similar to those seen in Galactic GMCs with OB star formation (presumably in the Galactic spiral arms). R2-1/1-0 is also high, similar to 0.8-1.0, in the central region of M51. Analysis of the molecular excitation using a Large Velocity Gradient radiative transfer calculation provides insight into the changes in the physical conditions of molecular gas between the arm and interarm regions: cold and low-density gas (less than or similar to 10 K, less than or similar to 300 cm(-3)) is required for the interarm GMCs, but this gas must become warmer and/or denser in the more active star-forming spiral arms. The ratio R2-1/1-0 is higher in areas of high 24 mu m dust surface brightness (which is an approximate tracer of star formation rate surface density) and high CO(1-0) integrated intensity (i.e., a well-calibrated tracer of total molecular gas surface density). The systematic enhancement of the CO(2-1) line relative to CO(1-0) in luminous star-forming regions suggests that some caution is needed when using CO(2-1) as a tracer of bulk molecular gas mass, especially when galactic structures are resolved.
  • Tatsuya Takekoshi, Tetsuhiro Minamidani, Shunichi Nakatsubo, Tai Oshima, Masayuki Kawamura, Hiroshi Matsuo, Tatsuhiro Sato, Nils W. Halverson, Adrian T. Lee, William L. Holzapfel, Yoichi Tamura, Akihiko Hirota, Kenta Suzuki, Takuma Izumi, Kazuo Sorai, Kotaro Kohno, Ryohei Kawabe
    IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY 2 (6) 584 - 592 2156-342X 2012/11 [Refereed][Not invited]
     
    Wideband continuum observations at the millimeter and submillimeter wavelengths are of great importance to the understanding of the cosmic history of star-formation across the Hubble time, as well as the thermal and non-thermal aspects of clusters of galaxies through the Sunyaev-Zel'dovich effect. To promote such studies, a new TES bolometer camera for the ASTE telescope has been developed. In this article we present the study of the optics system that will couple the camera to the telescope's Cassegrain optics. Two-color simultaneous observation capability and 7.5' diameter FoV are achieved. These two focal planes are used for the 270 and 350 GHz bands for Phase I, and the 350 and 670 GHz bands for Phase II configurations. The numbers of pixels are 169, 271, and 919 pixels for 270, 350, and 670 GHz bands, respectively. The shape of the third ellipsoid mirror is optimized, and the designed optics is foreseen to be diffraction limited. The optics is also evaluated via physical optics calculations, and the diameter of the cold pupil is optimized to 85% of the geometrical design. Without filters and Ruze losses, the aperture efficiencies of each beam are similar to 35%, 35%, and 32%, and the beam sizes are similar to 28 '', 22 '', and 12 '', for the 270, 350, and 670 GHz bands, respectively.
  • The remarkable blue-shift dominated jet in the high mass protostellar object G353.273+0.641
    Motogi, K, Sorai, K, Fujisawa, K, Sugiyama, K, Niinuma, K, Honma, M
    11th European VLBI Network Symposium & Users Meeting 1 - 5 2012/10 [Not refereed][Not invited]
  • Ohishi Yukie, Sorai Kazuo, Habe Asao
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN Astronomical Society of Japan 64 (4) "74 - 1"-"74-11" 0004-6264 2012/08/25 [Refereed][Not invited]
  • Motogi, Kazuhito, Sorai, Kazuo, Fujisawa, Kenta, Sugiyama, Koichiro, Honma, Mareki
    Cosmic Masers - from OH to H0, Proceedings of the International Astronomical Union, IAU Symposium 287 98 - 102 2012/07 [Not refereed][Not invited]
  • Sorai K, Kuno N, Nishiyama K, Watanabe Y, Matsui H, Habe A, Hirota A, Ishihara Y, Nakai N
    Publications of the Astronomical Society of Japan 64 51  2012/06 [Refereed][Not invited]
  • Matsui K, Sorai K, Watanabe Y, Kuno N
    Publications of the Astronomical Society of Japan 64 55  2012/06 [Refereed][Not invited]
  • Hiroyuki Nishitani, Kazuo Sorai, Asao Habe, Keita Hosaka, Yoshimasa Watanabe, Yukie Ohishi, Kazuhito Motogi, Tetsuhiro Minamidani, Masayuki Y. Fujimoto
    Publications of the Astronomical Society of Japan Astronomical Society of Japan 64 (2) 30 - 1"-"30-17" 0004-6264 2012/04 [Refereed][Not invited]
     
    We consider the properties of giant molecular cloud complexes in the star-forming region W 43 with a resolution of several pc scale, and discuss their relations to the evolutionary stages of massive star formation. We performed a NH<SUB>3</SUB> (J , K) = (1, 1), (2, 2), and (3, 3) inversion-line survey with the Hokkaido University 11-m telescope. Among 51 observed positions, selected based on integrated intensity maps of <SUP>13</SUP>CO (J = 1-0), these three emissions were detected from 21, 8, and 5 positions, respectively. The integrated intensity of the NH<SUB>3</SUB> (J , K) = (1, 1) line was found to be proportional to the far-infrared luminosity, estimated from IRAS data. The rotation temperatures were deduced to be ̃ 15-20 K at eight observed positions. In addition, the upper limits were estimated for 13 positions, which include the relatively low temperatures below 14 K at two positions with a relatively high fractions of NH<SUB>3</SUB> for <SUP>13</SUP>CO and with a low far-infrared luminosity. We derived the ortho-to-para abundance ratio of NH<SUB>3</SUB>. From the population distribution between the ortho- and para-levels of NH<SUB>3</SUB>, we also derived temperatures of ̃ 6-12 K, which may be interpreted as the temperatures when NH<SUB>3</SUB> molecules were formed. We discuss the relevance of the present results of our observations to the massive star-formation process and the current status of the W 43 region while taking into account previous observations of other indicators of massive star formation. It is shown that the complexes contain several regions in different evolutionary stages, or with the distinct characteristics of star formation within a timescales shorter than the lifetime of massive stars.
  • Tatsuya Takekoshi, Tetsuhiro Minamidani, Shunichi Nakatsubo, Tai Oshima, Masayuki Kawamura, Hiroshi Matsuo, Tatsuhiro Sato, Nils W. Halverson, Adrian T. Lee, William L. Holzapfel, Yoichi Tamura, Akihiko Hirota, Kenta Suzuki, Takuma Izumi, Kazuo Sorai, Kotaro Kohno, Ryohei Kawabe
    23rd International Symposium on Space Terahertz Technology 2012, ISSTT 2012 157 - 160 2012 
    Wideband and high spatial resolution continuum observations in the millimeter and submillimeter wavelengths are of great importance to understand star formation history of galaxies from distant to nearby (early to recent universe), and thermal and non-thermal aspects of clusters of galaxies through Sunyaev-Zel'dovich effect. To promote such studies based on the millimeter and submillimeter continuum data, new TES (Transition Edge Sensor) bolometer camera for the ASTE telescope has been developed. We aim to observe three bands, 1100μm, 850μm and 450μm. Camera optics is designed by geometrical optics to fit into the Cassegrain system of the ASTE telescope and the spatial limitation of its receiver cabin. For the efficient observation, our optics realizes 7.5′ field of view and 2-band simultaneous observation. The two focal planes can accommodate two of three TES bolometer wafers which have 169, 271, and 881 pixels at 1100, 850, and 450μm, respectively. The camera optics is accomplished diffraction limited optics, which is confirmed from spot diagrams and strehl ratios. It is evaluated via physical optics calculation, and all pixels on each focal plane have aperture efficiency of ∼30% in absence of reflection and absorption loss by filters and the Ruze loss. The dimensions of the optical elements are also determined based on the results of the physical optics calculations.
  • Akihiko Hirota, Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Kazuo Sorai
    AStrophysical Journal Letters 737 (1) 40  0004-637X 2011/11 [Refereed][Not invited]
     
    We present results of 12CO (1--0) and 13CO (1--0) observations of the
    northeastern spiral arm segment of IC 342 with a ~50pc resolution carried out
    with the Nobeyama Millimeter Array. Zero-spacing components were recovered by
    combining with the existing data taken with the Nobeyama 45m telescope. The
    objective of this study is to investigate the variation of cloud properties
    across the spiral arm with a resolution comparable to the size of giant
    molecular clouds (GMCs). The observations cover a 1 kpc times 1.5 kpc region
    located ~2 kpc away from the galactic center, where a giant molecular
    association is located at trailing side and associated star forming regions at
    leading side. The spiral arm segment was resolved into a number of clouds whose
    size, temperature and surface mass density are comparable to typical GMCs in
    the Galaxy. Twenty-six clouds were identified from the combined data cube and
    the identified clouds followed the line width-size relation of the Galactic
    GMCs. The identified GMCs were divided into two categories according to whether
    they are associated with star formation activity or not. Comparison between
    both categories indicated that the active GMCs are more massive, have smaller
    line width, and are closer to virial equilibrium compared to the quiescent
    GMCs. These variations of the GMC properties suggest that dissipation of excess
    kinetic energy of GMC is a required condition for the onset of massive star
    formation.
  • Motogi K, Sorai K, Honma M, Minamidani T, Takekoshi T, Akiyama K, Tateuchi K, Hosaka K, Ohishi Y, Watanabe Y, Habe A, Kobayashi H
    Monthly Notices of the Royal Astronomical Society 417 (1) 238 - 249 2011/10 [Refereed][Not invited]
  • Dense Clumps in Giant Molecular Clouds in the Large Magellanic Cloud: Density and Temperature Derived from 13CO(J = 3-2) Observations
    Minamidani, Tetsuhiro, Tanaka, Takanori, Mizuno, Yoji, Mizuno, Norikazu, Kawamura, Akiko, Onishi, Toshikazu, Hasegawa, Tetsuo, Tatematsu, Ken'ichi, Takekoshi, Tatsuya, Sorai, Kazuo, Moribe, Nayuta, Torii, Kazufumi, Sakai, Takeshi, Muraoka, Kazuyuki, Tanaka, Kunihiko, Ezawa, Hajime, Kohno, Kotaro, Kim, Sungeun, Rubio, Mónica, Fukui, Yasuo
    Astronomical Journal 141 (3) 73 - 84 2011/03/01 [Refereed][Not invited]
  • Watanabe Y, Sorai K, Kuno N, Habe A
    Monthly Notices of the Royal Astronomical Society 411 (3) 1409 - 1417 2011/03 [Refereed][Not invited]
  • Motogi K, Sorai K, Habe A, Honma M
    PASJ Astronomical Society of Japan 63 (1) 31 - 44 0004-6264 2011 [Refereed][Not invited]
  • Akihiko Hrota, Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Kazuo Sorai
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN 62 (5) 1261 - 1275 0004-6264 2010/10 [Refereed][Not invited]
     
    We present a (CO)-C-13 (1-0) mapping survey of the nearby galaxy IC 342 carried out with the Nobeyama 45 m radio telescope. The map covers a 320 '' x 320 '' region, including its center, bar, and most of one of the spiral arms. The (CO)-C-13 (1-0) data were compared with (CO)-C-12 (1-0), H alpha, 24 mu m, and K-s-band images to investigate spatial relations among molecular clouds, star-forming regions, and the stellar potential. The line ratio between both CO lines, I[(CO)-C-13 (1-0)]/I[(CO)-C-12 (1-0)] equivalent to R-13/12, was also derived to investigate the variation of molecular gas properties. The mean value of R-13/12 in the center of IC 342 is low (similar to 0.10 +/- 0.01) compared to the disk region (similar to 0.15 +/- 0.01). While R-13/12 in the central region is rather uniform, significant variations of R-13/12 were found in the spiral arms; that is, while it is low (similar to 0.1) at both ends of the bar and at the giant molecular cloud association (GMA) found in the spiral arm, it is high (0.14-0.20) downstream from the low R-13/12 region. The low- and high-R-13/12 regions in the disk correspond to the (CO)-C-12 peak and star-forming regions, respectively. The low R-13/12 in the galactic center is likely due to the higher gas temperature in the starburst region. The most probable explanation of the R-13/12 variation in the disk is that a low R-13/12 in the GMA and the ends of the bar reflects an increased fraction of the diffuse molecular component, which has a low column density and low volume density. Around the GMA and the north end of the bar, not only are the star-forming regions downstream from the CO distributions, but R-13/12 is also higher downstream, implying the presence of gas compression and ionized/molecular gas spatial offsets, as predicted by density wave models.
  • Akihiro Doi, Noriyuki Kawaguchi, Yusuke Kono, Tomoaki Oyama, Kenta Fujisawa, Hiroshi Takaba, Hiroshi Sudou, Ken-ichi Wakamatsu, Aya Yamauchi, Yasuhiro Murata, Nanako Mochizuki, Kiyoaki Wajima, Toshihiro Omodaka, Takumi Nagayama, Naomasa Nakai, Kazuo Sorai, Eiji Kawai, Mamoru Sekido, Yasuhiro Koyama, Shoichiro Asano, Hisao Uose
    Publications of the Astronomical Society of Japan 61 (6) 1389 - 1398 0004-6264 2009/12/25
  • Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Tsuyoshi Sawada, Kunihiko Tanaka, Toshihiro Handa, Masayuki Fukuhara, Hajime Ezawa, Ryohei Kawabe
    The Astrophysical Journal 706 (2) 1213 - 1225 0004-637X 2009/11/10
  • Akihiko Hirota, Nario Kuno, N. Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Hidenori Matsui, Asao Habe, Kazuo Sorai
    Publications of the Astronomical Society of Japan 61 (3) 441 - 450 0004-6264 2009/06/25
  • Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Toshihiro Handa, Kazuo Sorai, Sumio Ishizuki, Takeshi Okuda
    Publications of the Astronomical Society of Japan 61 (2) 163 - 176 0004-6264 2009/04/25
  • Kazuo Sorai, Asao Habe, Hiroyuki Nishitani, Keita Hosaka, Yoshimasa Watanabe, Shinichi Miwa, Yukie Ohishi, Kazuhito Motogi, Tetsuhiro Minamidani, Johta Awano, Sakurako Sumida, Yoshiaki Fukuya, Ryosuke Uchida, Noboru Kaneko, Masayuki Y. Fujimoto, Yasuhiro Koyama, Moritaka Kimura, Naomasa Nakai
    Publications of the Astronomical Society of Japan 60 (6) 1285 - 1296 0004-6264 2008/12/25
  • Takuma Suda, Yutaka Katsuta, Shimako Yamada, Tamon Suwa, Chikako Ishizuka, Yutaka Komiya, Kazuo Sorai, Masayuki Aikawa, Masayuki Y. Fujimoto
    Publications of the Astronomical Society of Japan 60 (5) 1159 - 1171 0004-6264 2008/10/25
  • Takumi Nagayama, Koji Takeda, Toshihiro Omodaka, Hiroshi Imai, Seiji Kameno, Yoshiaki Sofue, Akihiro Doi, Kenta Fujisawa, Asao Habe, Mareki Honma, Noriyuki Kawaguchi, Eiji Kawai, Hideyuki Kobayashi, Yasuhiro Koyama, Yasuhiro Murata, Kazuo Sorai, Hiroshi Sudou, Hiroshi Takaba, Sayaka Tamura, Ken-Ichi Wakamatsu
    Publications of the Astronomical Society of Japan 60 (5) 1069 - 1075 0004-6264 2008/10/25
  • K. Motogi, Y. Watanabe, K. Sorai, A. Habe, M. Honma, H. Imai, A. Yamauchi, H. Kobayashi, K. Fujisawa, T. Omodaka, H. Takaba, K. M. Shibata, T. Minamidani, K. Wakamatsu, H. Sudou, E. Kawai, Y. Koyama
    Monthly Notices of the Royal Astronomical Society 0035-8711 2008/09
  • Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Toshihito Shibatsuka
    Publications of the Astronomical Society of Japan 60 (3) 475 - 485 0004-6264 2008/06/25
  • Kotaro Kohno, Tomoka Tosaki, Rie Miura, Kazuyuki Muraoka, Tsuyoshi Sawada, Kouichiro Nakanishi, Nario Kuno, Takeshi Sakai, Kazuo Sorai, Kazuhisa Kamegai, Kunihiko Tanaka, Takeshi Okuda, Akira Endo, Bunyo Hatsukade, Masahiro Sameshima, Hajime Ezawa, Seiichi Sakamoto, Takeshi Kamazaki, Nobuyuki Yamaguchi, Juan CortÉs, Yoichi Tamura, Masayuki Fukuhara, Daisuke Iono, Ryohei Kawabe
    Publications of the Astronomical Society of Japan 60 (3) 457 - 464 0004-6264 2008/06/25
  • Akihiko Hirota, N. Kuno, N. Sato, T. Tosaki, H. Nakanishi, K. Sorai
    MAPPING THE GALAXY AND NEARBY GALAXIES 334 - 334 1570-6591 2008 [Refereed][Not invited]
  • Norio Kuno, N. Sato, H. Nakanishi, A. Hirota, T. Tosaki, Y. Shioya, K. Sorai, N. Nakai, K. Nishiyama, B. Vila-Vilaro
    MAPPING THE GALAXY AND NEARBY GALAXIES 170 - + 1570-6591 2008 [Refereed][Not invited]
     
    The results of a CO(1-0) mapping survey of 40 nearby spiral galaxies performed with the Nobeyama 45-m telescope are presented. The maps of CO cover most of the optical disk of the galaxies. We investigated the influence of bar on distribution of molecular gas in spiral galaxies using these data. We confirmed that the degree of central concentration is higher in barred spirals than in non-barred spirals as shown by previous works. Furthermore, we show that bars are efficient in driving molecular gas that lies within their radial scales toward the center, while the role in the accumulation from the larger spatial scales on the disks is small. The transported gas accounts for about half of molecular gas within the central region in barred spiral galaxies. We found a correlation between the degree of central concentration and bar strength. Galaxies with stronger bars tend to have higher central concentration. The correlation implies that stronger bars accumulate molecular gas toward the center more efficiently. These results are consistent with long-lived bars.
  • Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Seiichi Sakamoto
    MAPPING THE GALAXY AND NEARBY GALAXIES 357 - 357 1570-6591 2008 [Refereed][Not invited]
  • Sorai Kazuo, Kuno Nario, Nakai Naomasa, Matsui Hidenori, Habe Asao
    MAPPING THE GALAXY AND NEARBY GALAXIES 380  1570-6591 2008 [Refereed][Not invited]
  • Akihiro Doi, Kenta Fujisawa, Makoto Inoue, Kiyoaki Wajima, Hiroshi Nagai, Keiichiro Harada, Kousuke Suematsu, Asao Habe, Mareki Honma, Noriyuki Kawaguchi, Eiji Kawai, Hideyuki Kobayashi, Yasuhiro Koyama, Hiromitsu Kuboki, Yasuhiro Murata, Toshihiro Omodaka, Kazuo Sorai, Hiroshi Sudou, Hiroshi Takaba, Kazuhiro Takashima, Koji Takeda, Sayaka Tamura, Ken-ichi Wakamatsu
    Publications of the Astronomical Society of Japan 59 (4) 703 - 709 0004-6264 2007/08/25
  • Hiroshi Imai, Toshihiro Omodaka, Tomoya Hirota, Tomofumi Umemoto, Kazuo Sorai, Tetsuro Kondo
    Proceedings of the International Astronomical Union 3 (242) 340 - 341 1743-9213 2007/03 [Refereed][Not invited]
     
    We present H2O masers associated with the massive-star forming region G192 observed with the Japan VLBI network since the year 2005, The spatio-kinematical structure of the maser feature clusters has well persisted since previous observations, in which the masers are associated with two young stellar objects (YSOs) separated by ~1200 AU and expected to be associated with a highly-collimated bipolar jet and an infalling-rotating disk in the northern and southern YSOs, respectively. We estimated a jet speed of ~100 km s1 and re-estimated a dynamical age of the whole jet to be 5.6×104 years. The spatial distribution of maser Doppler velocities found during the previous and present observations, relative proper motions of H2O maser features in the southern cluster found in the present observations, a relative bulk motion between the two maser clusters are well explained by a model of an infalling-rotating disk with a radius of ~1000 AU and a central stellar mass of ~8 M. © 2008 International Astronomical Union.
  • Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Akihiko Hirota, Tomoka Tosaki, Yasuhiro Shioya, Kazuo Sorai, Naomasa Nakai, Kota Nishiyama, Baltsar Vila-VilarÓ
    Publications of the Astronomical Society of Japan 59 (1) 117 - 166 0004-6264 2007/02/25
  • Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Takeshi Okuda, Seiichi Sakamoto, Akira Endo, Bunyo Hatsukade, Kazuhisa Kamegai, Kunihiko Tanaka, Juan Cortes, Hajime Ezawa, Nobuyuki Yamaguchi, Takeshi Sakai, Ryohei Kawabe
    Publications of the Astronomical Society of Japan 59 (1) 43 - 54 0004-6264 2007/02/25
  • Nario Kuno, Koichiro Nakanishi, Kazuo Sorai, Toshihito Shibatsuka
    Astrophysics and Space Science Proceedings (202409) 379 - 382 1570-6605 2007 [Refereed][Not invited]
     
    We present results of CO observations of the barred spiral galaxy Maffei 2 with Nobeyama Millimeter Array (NMA). The distribution of the molecular gas in the central region shows elongated structure with two peaks as shown in the previous data. We found that the elongated structure resolved into spiral arms that continue from the offset ridges along the bar to a radius of less than 50 pc.
  • Kohno, K, Muraoka, K, Nakanishi, K, Tosaki, T, Kuno, N, Miura, R, Sawada, T, Sorai, K, Okuda, T, Kamegai, K, Tanaka, K, Endo, A, Hatsukade, B, Ezawa, H, Sakamoto, S, Cortes, J, Yamaguchi, N, Matsuo, H, Kawabe, R
    Proceedings of the International Astronomical Union 2, IAU Symposium #237 436 - 436 2007 [Not refereed][Not invited]
  • Hiroyuki Nakanishi, Nario Kuno, Yoshiaki Sofue, Naoko Sato, Naomasa Nakai, Yasuhiro Shioya, Tomoka Tosaki, Sachiko Onodera, Kazuo Sorai, Fumi Egusa, Akihiko Hirota
    The Astrophysical Journal 651 (2) 804 - 810 0004-637X 2006/11/10
  • Hiroshi Imai, Toshihiro Omodaka, Tomoya Hirota, Tomofumi Umemoto, Kazuo Sorai, Tetsuro Kondo
    Publications of the Astronomical Society of Japan 58 (5) 883 - 892 0004-6264 2006/10/25
  • K. Muraoka, K. Kohno, T. Tosaki, N. Kuno, K. Nakanishi, K. Sorai, S. Sakamoto
    Proceedings of the International Astronomical Union 2 (237) 451  1743-9213 2006/08 [Refereed][Not invited]
     
    We have performed CO(J=32) emission observations with the Atacama Submillimeter Telescope Experiment (ASTE) toward the 5 5 (or 6.6 6.6 kpc at the distance D = 4.5 Mpc) region of the nearby barred spiral galaxy M 83. We successfully resolved the major structures, i.e., the nuclear starburst region, bar, and inner spiral arms in CO(J=32) emission at a resolution of 22'' (or 480 pc), showing a good spatial coincidence between CO(J=32) and 6 cm continuum emissions. From a comparison of CO(J=32) data with CO(J=10) intensities measured with Nobeyama 45-m telescope, we found that the radial profile of CO(J=32)/CO(J=10) integrated intensity ratio R32/10 is almost unity in the central region (r< 0.25 kpc), whereas it drops to a constant value, 0.60.7, in the disk region. The radial profile of star formation efficiencies (SFEs), determined from 6 cm radio continuum and CO(J=10) emission, shows the same trend as that of R32/10. At the bar-end (r ~ 2.4 kpc), the amounts of molecular gas and the massive stars are enhanced when compared with other disk regions, whereas there is no excess of R32/10 and SFE in that region. This means that a simple summation of the star forming regions at the bar-end and the disk cannot reproduce the nuclear starburst of M 83, implying that the spatial variation of the dense gas fraction traced by R32/10 governs the spatial variation of SFE in M 83. © 2007 International Astronomical Union.
  • N. Kuno, N. Sato, H. Nakanishi, A. Hirota, T. Tosaki, Y. Shioya, K. Sorai, N. Nakai, K. Nishiyama, B. Vila-Vilaró
    Proceedings of the International Astronomical Union 2 (235) 116  1743-9213 2006/08 [Refereed][Not invited]
     
    We made a CO(1 - 0) mapping survey of 40 nearby spiral galaxies with the Nobeyama 45-m telescope to provide useful data for detailed and systematic studies of molecular gas in the galaxies (Kuno et al. 2006). Using these data we have compared the distribution of molecular gas in barred and non-barred spirals and investigated the influence of the bar. We confirmed that the degree of the central concentration of molecular gas within the radial distances of the order of a bar length in barred spirals is significantly higher than that in non-barred spirals as shown by Sakamoto et al. (1999) and Sheth et al. (2005). This is contrast with the degree of the concentration of the total molecular gas mass within the radial distances of the order of the bar, which is similar for both barred and non-barred spirals. This implies that the bars appear to be efficient in driving gas that lies within their radial scales toward the center of the host galaxies, but that they play quite a smaller role at larger spatial scales on the disks. Thus the characteristic feature of the radial distribution of molecular gas seen in barred spirals, i.e. the strong intensity peaks at their centers, the shallow gradients within the bar regions or/and the secondary peaks at the radius of the bar-ends, can be explained by the accumulation of molecular gas within the bar regions. The accumulated gas by bars accounts for about half of molecular gas mass within the central region. We also found a correlation between the degree of central concentration of molecular gas and the bar strength. Galaxies with stronger bars tend to have higher central concentrations. The result indicates that stronger bar accumulate molecular gas toward the center more efficiently. The correlation between the degree of central concentration of molecular gas and the strength seems to be consistent with long-lived bars rather than short-lived ones which are destroyed by the gas accumulation toward the center many times in the Hubble time.
  • Naoko Sato, Aya Yamauchi, Yuko Ishihara, Kazuo Sorai, Nario Kuno, Naomasa Nakai, Ramesh Balasubramanyam, Peter Hall
    Publications of the Astronomical Society of Japan 57 (4) 587 - 594 0004-6264 2005/08/25
  • Nario Kuno, Naomasa Nakai, Kazuo Sorai, Kohta Nishiyama, Baltasar Vila-VilarÓ
    Publications of the Astronomical Society of Japan 54 (4) 555 - 560 0004-6264 2002/08/25
  • Kazuo Sorai, Naomasa Nakai, Nario Kuno, Kohta Nishiyama
    Publications of the Astronomical Society of Japan 54 (2) 179 - 194 0004-6264 2002/04/25
  • Shin-ichiro Okumura, Ryosuke Miyawaki, Kazuo Sorai, Takuya Yamashita, Tetsuo Hasegawa
    Publications of the Astronomical Society of Japan 53 (5) 793 - 798 0004-6264 2001/10/25
  • Tsuyoshi Sawada, Tetsuo Hasegawa, Toshihiro Handa, Jun‐Ichi Morino, Tomoharu Oka, Roy Booth, Leonardo Bronfman, Masahiko Hayashi, Abraham Luna Castellanos, Lars‐Ake Nyman, Seiichi Sakamoto, Masumichi Seta, Peter Shaver, Kazuo Sorai, Kumiko Sato Usuda
    The Astrophysical Journal Supplement Series 136 (1) 189 - 219 0067-0049 2001/09
  • K. Sorai, T. Hasegawa, R. S. Booth, M. Rubio, J.‐I. Morino, L. Bronfman, T. Handa, M. Hayashi, L.‐A. Nyman, T. Oka, S. Sakamoto, M. Seta, K. S. Usuda
    The Astrophysical Journal 551 (2) 794 - 802 0004-637X 2001/04/20
  • Kazuo Sorai, Naomasa Nakai, Nario Kuno, Kohta Nishiyama, Tetsuo Hasegawa
    Publications of the Astronomical Society of Japan 52 (5) 785 - 802 0004-6264 2000/10/01
  • Nario Kuno, Kohta Nishiyama, Naomasa Nakai, Kazuo Sorai, Baltasar Vila-Vilaró, Toshihiro Handa
    Publications of the Astronomical Society of Japan 52 (5) 775 - 783 0004-6264 2000/10/01
  • Masumichi Seta, Tetsuo Hasegawa, T. M. Dame, Seiichi Sakamoto, Tomoharu Oka, Toshihiro Handa, Masahiko Hayashi, Jun‐Ichi Morino, Kazuo Sorai, Kumiko S. Usuda
    The Astrophysical Journal 505 (1) 286 - 298 0004-637X 1998/09/20
  • Seiichi Sakamoto, Toshihiro Handa, Yoshiaki Sofue, Mareki Honma, Kazuo Sorai
    The Astrophysical Journal 475 (1) 134 - 143 0004-637X 1997/01/20

MISC

  • 保田敦司, 久野成夫, 宮本祐介, SALAK Dragan, 中井直正, 中井直正, 瀬田益道, 永井誠, 石井峻, 渡邉祥正, 徂徠和夫, 徂徠和夫, 橋本拓也, 田中隆広, 保坂智哉  日本天文学会年会講演予稿集  2020-  2020
  • 渡邉祥正, 西村優里, 西村優里, 原田ななせ, 徂徠和夫, 坂井南美, 山本智  日本天文学会年会講演予稿集  2019-  2019
  • 喜多将一朗, 久野成夫, 田中隆広, 保田敦司, 小松崎龍聖, 渡邉祥正, 徂徠和夫, 矢島義之, 柴田修吾, 梶川明祐実, 八嶋裕, 宮本祐介, 金子紘之, 依田萌, 竹内努, 村岡和幸, 黒田麻友, 諸隈佳菜, 小林将人, SALAK Dragan, 野間勇斗, 瀬田益道, 中井直正, 中西裕之  日本天文学会年会講演予稿集  2019-  2019
  • 田中隆広, 久野成夫, 渡邉祥正, 廣田晶彦, 徂徠和夫, 矢島義之, 宮本祐介, 金子紘之, 竹内努, SALAK Dragan  日本天文学会年会講演予稿集  2019-  2019
  • 保田敦司, 久野成夫, 田中隆広, 渡邉祥正, 徂徠和夫, 矢島義之, 柴田修吾, 宮本祐介, 金子紘之, ESPADA Daniel, 村岡和幸, 黒田麻友, 依田萌, 竹内努, 諸隈佳菜, 小林将人, 中西裕之  日本天文学会年会講演予稿集  2019-  2019
  • 鳥居和史, 白崎裕治, ZAPART Christopher, 宮本祐介, 金子紘之, 徂徠和夫, 南谷哲宏, 梅本智文, 大石雅寿  日本天文学会年会講演予稿集  2018-  199  2018/02/20  [Not refereed][Not invited]
  • 佐藤佑哉, 久野成夫, 田中隆広, 保田敦司, 中井直正, 渡邉祥正, 徂徠和夫, 矢島義之, 柴田修吾, 金子紘之, 宮本祐介, 村岡和幸, 黒田麻友, 竹内努, 依田萌, SALAK Dragan, 野間勇斗, 中西裕之, 上野紗英子  日本天文学会年会講演予稿集  2018-  2018
  • 野間勇斗, SALAK Dragan, 瀬田益道, 中井直正, 徂徠和夫, 矢島義之, 柴田修吾, 梶川明祐実, 八嶋裕, 宮本祐介, 金子紘之, 久野成夫, 渡邉祥正, 田中隆広, 保田敦司, 喜多将一朗, 小松崎龍聖, 竹内努, 依田萌, 村岡和幸, 黒田麻友, 中西裕之, 大井渚, 諸隈佳菜, 松本尚子, PAN Hsi-An  日本天文学会年会講演予稿集  2018-  2018
  • 村岡和幸, 黒田麻友, 徂徠和夫, 矢島義之, 柴田修吾, 梶川明祐実, 八嶋裕, 久野成夫, 田中隆広, 保田敦司, 喜多将一朗, 小松崎龍聖, 渡邉祥正, 宮本祐介, 金子紘之, 依田萌, 竹内努, 諸隈佳菜, 小林将人, SALAK Dragan, 野間勇斗, 瀬田益道, 中井直正, 中西裕之  日本天文学会年会講演予稿集  2018-  2018
  • 矢島義之, 徂徠和夫, 徂徠和夫, 久野成夫, 村岡和幸, 竹内努, 宮本祐介, 金子紘之, 渡邉祥正, 小林将人, 田中隆広, 黒田麻友, 保田敦司, 依田萌, 柴田修吾  日本天文学会年会講演予稿集  2018-  2018
  • 泉奈都子, 大島泰, 竹腰達哉, 大田原一成, 石井峻, 荒井均, 廣田晶彦, 南谷哲宏, 岩下浩幸, 前川淳, 上水和典, 伊藤哲也, 藤井泰範, 斎藤智樹, 宮本祐介, 金子紘之, 諸隈佳菜, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 谷口暁星, 梅畑豪紀, LEE Minju, 山口裕貴, 安藤亮, 石田剛, 田村陽一, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 鈴木駿汰, 村岡和幸, 濤崎智佳, 小麥真也  日本天文学会年会講演予稿集  2017-  214  2017/02/28  [Not refereed][Not invited]
  • 大田原一成, 石井峻, 大島泰, 竹腰達哉, 泉奈都子, 上水和典, 伊藤哲也, 藤井泰範, 荒井均, 廣田晶彦, 南谷哲宏, 岩下浩幸, 前川淳, 斎藤智樹, 宮本祐介, 金子紘之, 諸隈佳菜, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 谷口暁星, 梅北豪紀, LEE Minju, 山口裕貴, 安藤亮, 石田剛, 田村陽一, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 鈴木駿汰, 村岡和幸, 濤崎智佳, 小麥真也  日本天文学会年会講演予稿集  2017-  213  2017/02/28  [Not refereed][Not invited]
  • 大島泰, 竹腰達哉, 大田原一成, 泉奈都子, 石井峻, 荒井均, 廣田晶彦, 南谷哲宏, 岩下浩幸, 前川淳, 上水和典, 伊藤哲也, 藤井泰範, 斎藤智樹, 宮本祐介, 金子紘之, 諸隈佳菜, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 谷口暁星, 梅畑豪紀, LEE Minju, 山口裕貴, 安藤亮, 石田剛, 田村陽一, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 鈴木駿汰, 村岡和幸, 濤崎智佳, 小麥真也  日本天文学会年会講演予稿集  2017-  213  2017/02/28  [Not refereed][Not invited]
  • 竹腰達哉, 大島泰, 大田原一成, 泉奈都子, 石井峻, 荒井均, 廣田晶彦, 南谷哲宏, 岩下浩幸, 前川淳, 上水和典, 伊藤哲也, 藤井泰範, 斎藤智樹, 宮本祐介, 金子紘之, 諸隈佳菜, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 谷口暁星, 梅畑豪紀, LEE Minju, 山口裕貴, 安藤亮, 石田剛, 田村陽一, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 鈴木駿汰, 村岡和幸, 濤崎智佳, 小麥真也  日本天文学会年会講演予稿集  2017-  213  2017/02/28  [Not refereed][Not invited]
  • 安藤亮, 中西康一郎, 河野孝太郎, 泉拓磨, MARTIN Sergio, MARTIN Sergio, 原田ななせ, 高野秀路, 久野成夫, 中井直正, 菅井肇, 徂徠和夫, 濤崎智佳, 松林和也, 中島拓, 田村陽一, 西村優里  日本天文学会年会講演予稿集  2017-  2017
  • 金子紘之, 宮本祐介, 徂徠和夫, 矢島義之, 柴田修吾, 中井直正, 久野成夫, 渡邉祥正, 田中隆広, 佐藤佑哉, 保田敦司, 大井渚, 諸隈佳菜, 竹内努, 依田萌, 村岡和幸, 黒田麻友, SALAK Dragan, 野間勇斗, 瀬田益道, 松本尚子, 中西裕之, 上野紗英子, PAN Hsi-An  日本天文学会年会講演予稿集  2017-  2017
  • 徂徠和夫, 久野成夫, 村岡和幸, 宮本祐介, 金子紘之, 中西裕之, 中井直正, 柳谷和希, 田中隆広, 佐藤佑哉, SALAK Dragan, 梅井迪子, 諸隈佳菜, 松本尚子, 上野紗英子, PAN Hsi-An, 野間勇斗, 竹内努, 依田萌, 黒田麻友, 保田敦司, 矢島義之, 大井渚, 柴田修吾, 瀬田益道, 渡邉祥正, 馬路博之, 瀬川陽子, 田代貴美, 武田美保, 岸田望美, 畠山拓也, 冨安悠人, 齊田智恵  日本天文学会年会講演予稿集  2017-  2017
  • 渡邉祥正, 西村優里, 西村優里, 坂井南美, 徂徠和夫, 原田ななせ, 久野成夫, 山本智  日本天文学会年会講演予稿集  2017-  2017
  • 黒田麻友, 村岡和幸, 徂徠和夫, 矢島義之, 柴田修吾, 中井直正, 久野成夫, 渡邉祥正, 田中隆広, 佐藤佑哉, 保田敦司, 諸隈佳菜, 宮本祐介, 金子紘之, 竹内努, 依田萌, SALAK Dragan, 野間勇斗, 松本尚子, 中西裕之, 上野紗英子, PAN Hsi-An  日本天文学会年会講演予稿集  2017-  2017
  • 安藤亮, 河野孝太郎, 田村陽一, 泉拓磨, 谷口暁星, 中西康一郎, 原田ななせ, 高野秀路, 中島拓, 徂徠和夫, 中井直正, 久野成夫, 菅井肇, 松林和也  日本天文学会年会講演予稿集  2016-  2016
  • 渡邉祥正, 西村優里, 坂井南美, 徂徠和夫, 原田ななせ, 山本智  日本天文学会年会講演予稿集  2016-  2016
  • 石井峻, 山口正行, 泉拓磨, 田村陽一, 河野孝太郎, 大島泰, 竹腰達哉, 大田原一成, 荒井均, 前川淳, 岩下浩幸, 佐藤立博, 廣田晶彦, 南谷哲宏, 松尾宏, 川邊良平, 鈴木駿汰, 村岡和幸, 中坪俊一, 森章一, 香内晃, 徂徠和夫  日本天文学会年会講演予稿集  2016-  2016
  • 山口正行, 山口正行, 大島泰, 竹腰達哉, 廣田晶彦, 大田原一成, 荒井均, 前川淳, 岩下浩幸, 佐藤立博, 南谷哲宏, 松尾宏, 川邊良平, 鈴木駿汰, 村岡和幸, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 泉拓磨, 田村陽一, 石井峻, 河野孝太郎  日本天文学会年会講演予稿集  2016-  2016
  • 大田原一成, 竹腰達哉, 大島泰, 上水和典, 伊藤哲也, 藤井泰範, 荒井均, 廣田晶彦, 岩下浩幸, 前川淳, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 石井峻, 田村陽一, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 鈴木駿汰, 村岡和幸  日本天文学会年会講演予稿集  2016-  2016
  • 鈴木駿汰, 村岡和幸, 大島泰, 竹腰達哉, 廣田晶彦, 大田原一成, 上水和典, 伊藤哲也, 荒井均, 藤井泰範, 岩下浩幸, 前川淳, 松尾宏, 川邊良平, 山口正行, 泉拓磨, 田村陽一, 石井峻, 河野孝太郎, 中坪俊一, 森章一, 香内晃, 徂徠和夫  日本天文学会年会講演予稿集  2016-  2016
  • 安藤亮, 河野孝太郎, 田村陽一, 泉拓磨, 梅畑豪紀, 永井洋, 徂徠和夫, 濤崎智佳  日本天文学会年会講演予稿集  2015-  2015
  • 渡邉祥正, 坂井南美, 徂徠和夫, 山本智  日本天文学会年会講演予稿集  2015-  2015
  • 渡邉祥正, 坂井南美, 徂徠和夫, 山本智  日本天文学会年会講演予稿集  2015-  2015
  • 川邊良平, 酒井剛, 田村陽一, 河野孝太郎, 徂徠和夫, 松原英雄, 奥村幸子, 大西利和, 大島泰, 野口卓, 高橋敏一  日本天文学会年会講演予稿集  2015-  2015
  • 中尾光, 渡辺誠, 徂徠和夫, 阿部祐平  日本天文学会年会講演予稿集  2015-  2015
  • 大島泰, 竹腰達哉, 荒井均, 前川淳, 岩下浩幸, 佐藤立博, 廣田晶彦, 南谷哲宏, 松尾宏, 川辺良平, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 泉拓磨, 石井峻, 田村陽一, 河野孝太郎  日本天文学会年会講演予稿集  2015-  2015
  • 諸隈佳菜, 徂徠和夫, 渡邉祥正, 久野成夫  日本天文学会年会講演予稿集  2014-  2014
  • 西村優里, 渡邉祥正, 坂井南美, 徂徠和夫, 山本智  日本天文学会年会講演予稿集  2014-  2014
  • 徂徠和夫, 羽部朝男, 日浦皓一朗, 梅井迪子, 西川由恭, 岸田望美, 中島大貴, 南原甫幸, 渡邉祥正, 元木業人, 西谷洋之, 南谷哲宏, 諸隈佳菜, 竹腰達哉  日本天文学会年会講演予稿集  2014-  2014
  • 大島泰, 竹腰達哉, 荒井均, 前川淳, 岩下浩幸, 佐藤立博, 廣田晶彦, 南谷哲宏, 松尾宏, 川辺良平, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 泉拓磨, 石井峻, 田村陽一, 河野孝太郎  日本天文学会年会講演予稿集  2014-  2014
  • 竹腰達哉, 大島泰, 荒井均, 前川淳, 岩下浩幸, 佐藤立博, 廣田晶彦, 南谷哲宏, 松尾宏, 川辺良平, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 泉拓磨, 石井峻, 田村陽一, 河野孝太郎  日本天文学会年会講演予稿集  2014-  2014
  • 荒井均, 大島泰, 竹腰達哉, 前川淳, 岩下浩幸, 佐藤立博, 廣田晶彦, 南谷哲宏, 松尾宏, 川辺良平, 中坪俊一, 森章一, 香内晃, 徂徠和夫, 泉拓磨, 石井峻, 田村陽一, 河野孝太郎  日本天文学会年会講演予稿集  2014-  2014
  • WATANABE Yoshimasa, SAKAI Nami, SORAI Kazuo, YAMAMOTO Satoru  日本天文学会年会講演予稿集  2013-  2013
  • WATANABA Yoshimasa, SAKAI Nami, SORAI Kazuo, YAMAMOTO Satoru  日本天文学会年会講演予稿集  2012-  2012
  • 中尾光, 徂徠和夫, 渡辺誠, 山田真広, 伊藤洋一, 宮田隆志, 酒向重行  日本天文学会年会講演予稿集  2012-  2012
  • 中尾光, 渡辺誠, 徂徠和夫, 山田真広, 伊藤洋一, 宮田隆志, 酒向重行  日本天文学会年会講演予稿集  2012-  2012
  • Akihiro Doi, Kotaro Kohno, Kouichiro Nakanishi, Seiji Kameno, Makoto Inoue, Kazuhiro Hada, Kazuo Sorai  2011/06/15  [Not refereed][Not invited]
     
    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak
    radio continuum emission at the galactic center. Quasi-simultaneous
    multi-frequency observations using the Very Large Array (VLA) from 5 GHz (6 cm)
    to 22 GHz (1.3 cm) showed inverted spectra in all epochs, which were
    intra-month variable, as well as complicated spectral features that cannot be
    represented by a simple power law, indicating multiple blobs in nuclear jets.
    Using the Nobeyama Millimeter Array (NMA), we discovered a large amplitude
    variable emission at 100 GHz (3 mm), which had higher flux densities at most
    epochs than those of the VLA observations. A James Clerk Maxwell Telescope
    (JCMT) observation at 347 GHz (850 micron) served an upper limit of dust
    contamination. The inverted radio spectrum of the nucleus NGC 4258 is
    suggestive of an analogy to our Galactic center Sgr A*, but with three orders
    of magnitude higher radio luminosity. In addition to the LLAGN M 81, we discuss
    the nucleus of NGC 4258 as another up-scaled version of Sgr A*.
  • 渡辺誠, 高橋幸弘, 渡部重十, 佐藤光輝, 福原哲也, 濱本昂, 徂徠和夫, 中尾光, 田中培生, 館内謙, 関口朋彦  日本天文学会年会講演予稿集  2011-  2011
  • 中尾光, 徂徠和夫, 渡辺誠, 山田真広, 伊藤洋一, 酒向重行, 宮田隆志  日本天文学会年会講演予稿集  2011-  2011
  • 中尾光, 徂徠和夫, 渡辺誠, 山田真広, 伊藤洋一, 酒向重行, 宮田隆志  日本天文学会年会講演予稿集  2011-  2011
  • 山田真広, 伊藤洋一, 中尾光, 徂徠和夫, 渡辺誠, 酒向重行, 宮田隆志  日本天文学会年会講演予稿集  2011-  2011
  • 徂徠和夫, 渡邉祥正, 羽部朝男, 久野成夫  日本天文学会年会講演予稿集  2010-  2010
  • 松井佳菜, 徂徠和夫, 渡邉祥正  日本天文学会年会講演予稿集  2010-  2010
  • 舘内謙, 秋山和徳, 中尾光, 徂徠和夫, 羽部朝男, 南谷哲宏, 西谷洋之, 保坂啓太, 渡邊祥正, 大石晋恵, 元木業人, 松井佳奈, 竹腰達哉, 相良啓介  日本天文学会年会講演予稿集  2010-  2010
  • 南谷哲宏, 竹腰達哉, 徂徠和夫, 河村晶子, 福井康雄, 大西利和, 水野範和  日本天文学会年会講演予稿集  2010-  2010
  • 大石晋恵, 徂徠和夫, 南谷哲宏, 西谷洋之, 渡邉祥正, 保坂啓太, 松井佳菜, 元木業人, 竹腰達哉, 相良啓介  日本天文学会年会講演予稿集  2010-  2010
  • 竹腰達哉, 南谷哲宏, 中坪俊一, 徂徠和夫, 川村雅之, 河野孝太郎, 大島泰, 田村陽一, 江澤元, 川辺良平  日本天文学会年会講演予稿集  2010-  2010
  • 竹腰達哉, 南谷哲宏, 徂徠和夫, 水野範和, 水野陽治, 村井美幸, 洞地博隆, 河村晶子, 福井康雄, 大西利和  日本天文学会年会講演予稿集  2010-  2010
  • 南谷哲宏, 竹腰達哉, 徂徠和夫, 河村晶子, 福井康雄, 大西利和, 水野範和, KIM S.  日本天文学会年会講演予稿集  2010-  2010
  • 渡辺祥正, 徂徠和夫, 南谷哲宏, 久野成夫, 濤崎智佳  日本天文学会年会講演予稿集  2009-  2009
  • 渡辺祥正, 徂徠和夫, 南谷哲宏, 久野成夫, 濤崎智佳  日本天文学会年会講演予稿集  2009-  2009
  • 竹腰達哉, 南谷哲宏, 徂徠和夫, 水野範和, 濤崎智佳, 水野陽治, 村井美幸, 洞地博隆, 河村晶子, 大西利和, 福井康雄, 河野孝太郎, 小麦真也, RUBIO Monica, RUBIO Monica  日本天文学会年会講演予稿集  2009-  2009
  • 元木業人, 徂徠和夫, 南谷哲宏, 西谷洋之, 保坂啓太, 渡邉祥正, 大石晋恵, 松井佳菜, 竹腰達哉, 相良啓介, 羽部朝男, 藤本正行  日本天文学会年会講演予稿集  2009-  2009
  • 南谷哲宏, 竹腰達哉, 徂徠和夫, 水野範和, 大西利和, 河村晶子, 福井康雄, RUBIO Monica  日本天文学会年会講演予稿集  2009-  2009
  • 竹腰達哉, 南谷哲宏, 徂徠和夫, 川村雅之, 河野孝太郎, 大島泰, 田村陽一, 江澤元, 川辺良平  日本天文学会年会講演予稿集  2009-  2009
  • 徂徠和夫, 羽部朝男, 西谷洋之, 保坂啓太, 渡邉祥正, 大石晋恵, 元木業人, 南谷哲宏, 松井佳菜, 竹腰達哉, 藤本正行  日本天文学会年会講演予稿集  2008-  2008
  • 南谷哲宏, 竹腰達哉, 三輪真一, 西谷洋之, 保坂啓太, 渡邉祥正, 大石晋恵, 元木業人, 松井佳菜, 清水宏人, 徂徠和夫, 羽部朝男, 藤本正行, 木村公洋, 小川英夫  日本天文学会年会講演予稿集  2008-  2008
  • 竹腰達哉, 徂徠和夫, 西谷洋之, 保坂啓太, 大石晋恵, 元木業人, 南谷哲宏, 羽部朝男  日本天文学会年会講演予稿集  2008-  2008
  • 元木業人, 渡邉祥正, 徂徠和夫, 羽部朝男, 南谷哲宏, 本間希樹, 小林秀行, 柴田克典, 藤澤健太, 面高俊宏, 今井裕, 若松謙一, 高羽浩, 須藤広志, 村田泰宏, 川合栄治, 久保木裕充  日本天文学会年会講演予稿集  2007-  2007
  • 保坂啓太, 徂徠和夫, 羽部朝男, 内田亮輔, 粟野穰太, 西谷洋之, 渡辺祥正, 三輪真一, 藤本正行  日本天文学会年会講演予稿集  2006-  2006
  • 徂徠和夫, 羽部朝男, 粟野穰太, 西谷洋之, 保坂啓太, 渡邉祥正, 三輪真一, 大石晋恵, 元木業人, 住田桜子, 福谷義明, 内田亮輔, 兼古昇, 藤本正行  日本天文学会年会講演予稿集  2006-  2006
  • 西谷洋之, 徂徠和夫, 羽部朝男, 粟野穰太, 保坂啓太, 渡邉祥正, 三輪真一, 藤本正行  日本天文学会年会講演予稿集  2006-  2006
  • H Nakanishi, N Kuno, Y Sofue, N Sato, N Nakai, Y Shioya, T Tosaki, S Onodera, K Sorai, F Egusa, A Hirota  PROCEEDINGS OF THE DUSTY AND MOLECULAR UNIVERSE: A PRELUDE TO HERSCHEL AND ALMA  577-  301  -302  2005  [Not refereed][Not invited]
     
    We present the results of (CO)-C-12(J = 1 - 0) observations of five Virgo spiral galaxies obtained with the Nobeyama 45-m telescope equipped with a multibeam receiver, BEARS. We combined the CO data with H I data to address environmental effect on gaseous disks. We investigated a relationship between the molecular fraction (f(mol)) and the total gaseous density, (H I plus H-2 density, Sigma(HI+H2)). We found that three of our samples display unusually larger f(mol) than that expected for the field galaxies, while the rest two galaxies show the normal f(mol). It implies that the ram-pressure stripping occurs at the inner disks to result in unusually large f(mol) as one possibility.
  • 西谷洋之, 徂徠和夫, 羽部朝男, 粟野穣太, 内田亮輔, 保坂啓太, 渡邉祥正, 住田桜子, 福谷義明, 兼古昇, 藤本正行  日本天文学会年会講演予稿集  2005-  2005
  • 徂徠和夫, 羽部朝男, 粟野穣太, 住田桜子, 福谷義明, 内田亮輔, 西谷洋之, 保坂啓太, 渡邉祥正, 兼古昇, 藤本正行  日本天文学会年会講演予稿集  2005-  2005
  • VLBI Observation of Spacecraft for Navigation
    Mamoru Sekido, Ryuichi Ichikawa, Hiroshi Takeuchi, Yasuhiro Koyama, Eiji Kawai, Tetsuro Kondo, Makoto Yoshikawa, Nanako Mochizuki, Yasuhiro Murata, Takaji Kato, Tsutomu Ichikawa, Hisashi Hirabayashi, Takafumi Ohnishi, Fuyuhiko Kikuchi, Kazuhiro Takashima, Kenta Fujisawa, Hiroshi Takaba, Kazuo Sorai, Wayne Cannon, Sasha Novikov, Mario Berube  URSI-General Assembly, 2005 Oct. New Delih India  2005  [Not refereed][Not invited]
  • SEKIGUCHI Tomohiko, HASEGAWA Tetsuo, KOUCHI Akira, SORAI Kazuo, SAKAMOTO Seiichi  Planetary people  12-  (2)  96  -107  2003/06/25
  • Nobeyama CO Atlas of Nearby Spiral Galaxies
    Nario Kuno, Naomasa Nakai, Kazuo Sorai, Naoko Sato, Aya Ymauchi, Tomoka Tosaki, Yoshiyuki Shioya, Baltasar Vila-Vilaró, Kohta Nishiyama, Yuko Ishihara, J. Cepa  ASP Conference Proceedings 249, The Central Kiloparsec of Starbursts and AGN: The La Palma Connection, editted by J. H. Knapen, J. E. Beckman, I. Shlosman, T. J. Mahoney  71  -72  2003  [Not refereed][Not invited]
  • Physical Conditions and Structure of Molecular Gas in the Galactic Center
    Tsuyoshi Sawada, Tetsuo Hasegawa, Toshihiro Handa, Jun-Ichi Morino, Kumiko S. Usuda, Kazuo Sorai, Tomoharu Oka, Masumichi Seta, Seiichi Sakamoto, Masahiko Hayashi, Roy Booth, Leonard Bronfman, Abraham L. Castellanos, Lars-Åke Nyman, Peter Shaver, R. J. Cohen  ASP Conference Proceedings 289, The Proceedings of the IAU 8th Asian-Pacific Regional Meeting, editted by S. Ikeuchi, J. Hearnshaw, and T. Hanawa, the Astronomical Society of Japan  207  -208  2003  [Not refereed][Not invited]
  • Nobeyama CO Atlas of Nearby Spiral Galaxies
    Nario Kuno, Naomasa Nakai, Kazuo Sorai, Naoko Sato, Aya Ymauchi, Tomoka Tosaki, Yoshiyuki Shioya, Baltasar Vila-Vilaró, Kohta Nishiyama, Yuko Ishihara, J. Cepa  ASP Conference Proceedings 249, The Central Kiloparsec of Starbursts and AGN: The La Palma Connection, editted by J. H. Knapen, J. E. Beckman, I. Shlosman, T. J. Mahoney  71  -72  2003  [Not refereed][Not invited]
  • FUJISAWA K.  Journal of the Communications Research Laboratory  48-  (46)  47  -58  2001  [Not refereed][Not invited]
  • N Kuno, K Nishiyama, N Nakai, K Sorai, B Vila-Vilaro, T Handa  GALAXY DISKS AND DISK GALAXIES  230-  379  -380  2001  [Not refereed][Not invited]
     
    We present the results of the CO mapping observations of the barred spiral galaxy NGC 3504 with the Nobeyama 45-m telescope. The distribution of the molecular gas shows offset ridges which correspond to the distribution of H II regions along the bar. The velocity perpendicular to the bar decreases abruptly at the ridge. We propose new method to derive the pattern speed of the bar.
  • K Sorai, N Nakai, K Nishiyama  GALAXY DISKS AND DISK GALAXIES  230-  385  -386  2001  [Not refereed][Not invited]
     
    We observed HCN (J=1-0) and (CO)-C-13 (J=1-0) simultaneously toward the nuclear region and the disk of the nearby barred spiral galaxy NGC 253 and compared with (CO)-C-12 (J=1-0) data. The HCN/(CO)-C-13 and HCN/(CO)-C-12 ratios are higher in the nuclear region than those in the disk, which indicates that the molecular gas in the nuclear region is dense and hot, while less dense in the disk, based on the one-zone large velocity gradient model. We also observed HCN and (CO)-C-12 simultaneously along the major axes of nearby CO bright galaxies.
  • N Kuno, N Nakai, B Vila-Vilaro, K Nishiyama, K Sorai  CENTRAL KILOPARSEC OF STARBURSTS AND AGN: THE LA PALMA CONNECTION  249-  695  -698  2001  [Not refereed][Not invited]
     
    We present the results of CO and HCN observations of the early-type galaxies NGC 404, NGC 3593, and NGC 4293, using the Nobeyama 45 m telescope. We detected HCN emission from NGC 3593 and NGC 4293. The HCN emission profiles show large differences from the profiles of CO emission. The HCN emission is weak at the systemic velocity of these galaxies, while the CO emission has a peak at this velocity. The HCN/CO intensity ratios in these galaxies are comparable to those of late-type spirals. We present also the preliminary results of high-resolution observations of NGC 4293 with the Nobeyama Millimeter Array (NMA).
  • N Kuno, K Nishiyama, N Nakai, K Sorai, B Vila-Vilaro, T Handa  GALAXY DISKS AND DISK GALAXIES  230-  379  -380  2001  [Not refereed][Not invited]
     
    We present the results of the CO mapping observations of the barred spiral galaxy NGC 3504 with the Nobeyama 45-m telescope. The distribution of the molecular gas shows offset ridges which correspond to the distribution of H II regions along the bar. The velocity perpendicular to the bar decreases abruptly at the ridge. We propose new method to derive the pattern speed of the bar.
  • HCN/CO Ratio in the Nuclear Regions and the Disks of Nearby Spiral Galaxies
    Kazuo Sorai, Naomasa Nakai, Nario Kuno, Kohta Nishiyama  ASP Conference Series 230, Galaxy Disks and Disk Galaxies, editted by J. G. Funes, S. J. and E. M. Corsini  385  -386  2001  [Not refereed][Not invited]
  • N Kuno, N Nakai, B Vila-Vilaro, K Nishiyama, K Sorai  CENTRAL KILOPARSEC OF STARBURSTS AND AGN: THE LA PALMA CONNECTION  249-  695  -698  2001  [Not refereed][Not invited]
     
    We present the results of CO and HCN observations of the early-type galaxies NGC 404, NGC 3593, and NGC 4293, using the Nobeyama 45 m telescope. We detected HCN emission from NGC 3593 and NGC 4293. The HCN emission profiles show large differences from the profiles of CO emission. The HCN emission is weak at the systemic velocity of these galaxies, while the CO emission has a peak at this velocity. The HCN/CO intensity ratios in these galaxies are comparable to those of late-type spirals. We present also the preliminary results of high-resolution observations of NGC 4293 with the Nobeyama Millimeter Array (NMA).
  • H Kiuchi, Y Takahashi, A Kaneko, H Uose, S Iwamura, T Hoshino, N Kawaguchi, H Kobayashi, K Fujisawa, J Amagai, J Nakajima, T Kondo, S Iguchi, T Miyaji, K Sorai, K Sebata, T Yoshino, N Kurihara  IEICE TRANSACTIONS ON COMMUNICATIONS  E83B-  (2)  238  -245  2000/02  [Not refereed][Not invited]
     
    The Communications Research Laboratory (CRL), the National Astronomical Observatory (NAO), the Institute of Space and Astronoutical Science (ISAS), and the Telecommunication Network Laboratory Group of Nippon Telegraph and Telephone Corporation (NTT) have developed a very-long-baseline-connected-interferometry array, maximum baseline-length was 208 km, using a highspeed asynchronous transfer mode (ATM) network with an AAL1 that corresponds to the constant bit-rate protocol. The very long baseline interferometry (VLBI) observed data is transmitted through a 2.488-Gbps [STM-16/OC-48] ATM network instead of being recorded onto magnetic tape. By combining antennas via a high-speed ATM network, a highly-sensitive virtual (radio) telescope system was realized. The system was composed of two real-time VLBI networks: the Kry-Stone-Project (KSP) network of CRL (which is used for measuring crustal deformation in the Tokyo metropolitan area), and the OLIVE (optically linked VLBI experiment) network of NAO and ISAS which is used for astronomy (space-VLBI). These networks operated in cooperation with NTT. In order to realize a virtual telescope, the acquired VLBI data were corrected via the ATM networks and were synthesized using the VLBI technique. The cross-correlation processing and data observation were done simultaneously in this system and radio flares on the weak radio source (HR1099) were detected.
  • K Sorai, K Sunada, SK Okumura, T Iwasa, A Tanaka, K Natori, H Onuki  RADIO TELESCOPES  4015-  86  -95  2000  [Not refereed][Not invited]
     
    New digital spectrometers for the 25-BEam Array Receiver System (BEARS) of the Nobeyama 45-m telescope are described. A commercial digital oscilloscope is used as a digitizer. The digitizer samples analogue data with 2 bits (4 levels). Data of 512 MHz bandwidth are processed for four beams at the same time. The data-formatting unit demultiplexes 2 bits 8 data in parallel to 32 parallels and sends outputs to LSIs. General purpose LSIs for autocorrelation read the digital data with a clock rate of 32 MHz. Thirty-two LSIs of 32 lags connected in cascades calculate 1024-lag autocorrelation, and output a 1024-channel power spectrum of 512 MHz bandwidth. The bandwidth of 32 MHz is achieved by picking up the data in a rate of 1/16 in the front part of the autocorrelator module. The total performances have been demonstrated by long-term integration of noise signals from receivers and observations of the Galactic star-forming region W51 in CO line.
  • K Sunada, C Yamaguchi, N Nakai, K Sorai, SK Okumura, N Ukita  RADIO TELESCOPES  4015-  237  -246  2000  [Not refereed][Not invited]
     
    A large focal plane array receiver system for the NRO 45m telescope ISIS 25-BEam array Receiver System, or BEARS) is described. This new array receiver uses SIS junctions and has 25 elements. It can operate at the frequency range of 82 - 116 GHz. The development of this new system is almost complete. We describe about the whole system in detail, which includes the receiver, the IF systems, the new spectrometers and the remote control systems. We also describe about the performances and the uniformity of the system and show the astronomical result.
  • 山口伸行, 大西利和, 早川貴敬, 徂徠和夫, 浮田信治, 立松健一, 江澤元, 砂田和良  日本天文学会年会講演予稿集  2000-  2000
  • Low Density Molecular Gas in the Galaxy
    Kumiko S. Usuda, Tetsuo Hasegawa, Toshihiro Handa, Jun-Ichi Morino, Tuyoshi Sawada, Seiichi Sakamoto, Tomoharu Oka, Masumichi Seta, Kazuo Sorai, Masahiko Hayashi, Roy Booth, Lars-Åke Nyman, Leonardo Bronfman, Jorge May, Abraham Luna, Peter Shaver, Glenn J. White  Proceedings of the 3rd Cologne-Zermatt Symposium, The Physics and Chemistry of the Interstellar Medium, edited by V. Ossenkopf, J. Stuzki, G. Winnewisser  96  1999  [Not refereed][Not invited]
  • S Sakamoto, T Hasegawa, T Handa, JI Morino, T Oka, M Seta, K Sorai, KS Usuda, M Hayashi  NEW PERSPECTIVES ON THE INTERSTELLAR MEDIUM  168-  90  -93  1999  [Not refereed][Not invited]
     
    We have conducted an extensive CO J=2-1 survey of the northern Galactic plane with the same angular resolution as the CfA CO J=1-0 survey to extract physical conditions of the molecular gas. The CO J=2-1/J=1-0 intensity ratio (= R2-1/1-0) shows a large-scale radial gradient from similar to 0.70 at 4 kpc to similar to 0.55 at 8 kpc Galactocentric distance. The observed large-scale radial decrease in R2-1/1-0 is ascribed to a change in the fraction of the gas with high R2-1/1-0 (dense gas) from similar to 40% near 5 kpc to similar to 20% near the solar circle. Molecular gas with higher R2-1/1-0 is found predominantly along the Sagittarius and Scutum arms, probably in their downstream. This implies that physical conditions of interstellar gas, density in particular, are affected by grand-design, nonlinear processes, such as gravitational collapse induced by spiral density waves.
  • Molecular Gas in the Galactic Center: Large-Scale Structure and Kinematics
    Tsuyoshi Sawada, Tetsuo Hasegawa, Toshihiro Handa, Jun-Ichi Morino, Kumiko S. Usuda, Kazuo Sorai, Tomoharu Oka, Masumichi Seta, Seiichi Sakamoto, Masahiko Hayashi, Roy Booth, Leonard Bronfman, Abraham C. Luna, Lars-Åke Nyman  Proceedings Of Star Formation 1999, editted by T. Nakamoto and Nobeyama Radio Observatory  104  -105  1999  [Not refereed][Not invited]
  • T Sawada, T Hasegawa, T Handa, KS Usuda, JI Morino, R Booth, L Bronfman, A Luna, M Hayashi, LA Nyman, T Oka, S Sakamoto, M Seta, P Shaver, K Sorai  AGN/NORMAL GALAXY CONNECTION  23-  (5/6)  985  -989  1999  [Not refereed][Not invited]
     
    We have observed the Galactic center in (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) lines using the Tokyo-Onsala-ESO-Calan 60-cm telescope and compared the data with the (CO)-C-12(J = 1-0) Columbia survey (Bitran et al. 1997). The (CO)-C-12 J = 2-1/J = 1-0 intensity ratio is very high (0.96) in the central 900 pc of the Galaxy, although it is about 0.6-0.7 for typical molecular clouds in the Galactic disk. The observed intensity ratios, (CO)-C-12 J = 2-1/J = 1-0 and (CO)-C-13/(CO)-C-12 (J = 2-1), indicate that even the (CO)-C-12 line is not very optically thick: tau(12CO(J=1-0)) similar to 1 or smaller in the Galactic center. This may be due to high temperature and large velocity dispersion. The large velocity dispersion is probably caused by large external pressure and tidal forces. (C)1999 COSPAR. Published by Elsevier Science Ltd.
  • Low Density Molecular Gas in the Galaxy
    Kumiko S. Usuda, Tetsuo Hasegawa, Toshihiro Handa, Jun-Ichi Morino, Tuyoshi Sawada, Seiichi Sakamoto, Tomoharu Oka, Masumichi Seta, Kazuo Sorai, Masahiko Hayashi, Roy Booth, Lars-Åke Nyman, Leonardo Bronfman, Jorge May, Abraham Luna, Peter Shaver, Glenn J. White  Proceedings of the 3rd Cologne-Zermatt Symposium, The Physics and Chemistry of the Interstellar Medium, edited by V. Ossenkopf, J. Stuzki, G. Winnewisser  96  1999  [Not refereed][Not invited]
  • S Sakamoto, T Hasegawa, T Handa, JI Morino, T Oka, M Seta, K Sorai, KS Usuda, M Hayashi  NEW PERSPECTIVES ON THE INTERSTELLAR MEDIUM  168-  90  -93  1999  [Not refereed][Not invited]
     
    We have conducted an extensive CO J=2-1 survey of the northern Galactic plane with the same angular resolution as the CfA CO J=1-0 survey to extract physical conditions of the molecular gas. The CO J=2-1/J=1-0 intensity ratio (= R2-1/1-0) shows a large-scale radial gradient from similar to 0.70 at 4 kpc to similar to 0.55 at 8 kpc Galactocentric distance. The observed large-scale radial decrease in R2-1/1-0 is ascribed to a change in the fraction of the gas with high R2-1/1-0 (dense gas) from similar to 40% near 5 kpc to similar to 20% near the solar circle. Molecular gas with higher R2-1/1-0 is found predominantly along the Sagittarius and Scutum arms, probably in their downstream. This implies that physical conditions of interstellar gas, density in particular, are affected by grand-design, nonlinear processes, such as gravitational collapse induced by spiral density waves.
  • T Sawada, T Hasegawa, T Handa, KS Usuda, JI Morino, R Booth, L Bronfman, A Luna, M Hayashi, LA Nyman, T Oka, S Sakamoto, M Seta, P Shaver, K Sorai  AGN/NORMAL GALAXY CONNECTION  23-  (5/6)  985  -989  1999  [Not refereed][Not invited]
     
    We have observed the Galactic center in (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) lines using the Tokyo-Onsala-ESO-Calan 60-cm telescope and compared the data with the (CO)-C-12(J = 1-0) Columbia survey (Bitran et al. 1997). The (CO)-C-12 J = 2-1/J = 1-0 intensity ratio is very high (0.96) in the central 900 pc of the Galaxy, although it is about 0.6-0.7 for typical molecular clouds in the Galactic disk. The observed intensity ratios, (CO)-C-12 J = 2-1/J = 1-0 and (CO)-C-13/(CO)-C-12 (J = 2-1), indicate that even the (CO)-C-12 line is not very optically thick: tau(12CO(J=1-0)) similar to 1 or smaller in the Galactic center. This may be due to high temperature and large velocity dispersion. The large velocity dispersion is probably caused by large external pressure and tidal forces. (C)1999 COSPAR. Published by Elsevier Science Ltd.
  • Molecular Gas in the Galactic Center: Large-Scale Structure and Kinematics
    Tsuyoshi Sawada, Tetsuo Hasegawa, Toshihiro Handa, Jun-Ichi Morino, Kumiko S. Usuda, Kazuo Sorai, Tomoharu Oka, Masumichi Seta, Seiichi Sakamoto, Masahiko Hayashi, Roy Booth, Leonard Bronfman, Abraham C. Luna, Lars-Åke Nyman  Proceedings Of Star Formation 1999, editted by T. Nakamoto and Nobeyama Radio Observatory  104  -105  1999  [Not refereed][Not invited]
  • T Sawada, T Hasegawa, T Handa, KS Usuda, JI Morino, R Booth, L Bronfman, A Luna, M Hayashi, LA Nyman, T Oka, S Sakamoto, M Seta, P Shaver, K Sorai  AGN/NORMAL GALAXY CONNECTION  23-  (5/6)  985  -989  1999  [Not refereed][Not invited]
     
    We have observed the Galactic center in (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) lines using the Tokyo-Onsala-ESO-Calan 60-cm telescope and compared the data with the (CO)-C-12(J = 1-0) Columbia survey (Bitran et al. 1997). The (CO)-C-12 J = 2-1/J = 1-0 intensity ratio is very high (0.96) in the central 900 pc of the Galaxy, although it is about 0.6-0.7 for typical molecular clouds in the Galactic disk. The observed intensity ratios, (CO)-C-12 J = 2-1/J = 1-0 and (CO)-C-13/(CO)-C-12 (J = 2-1), indicate that even the (CO)-C-12 line is not very optically thick: tau(12CO(J=1-0)) similar to 1 or smaller in the Galactic center. This may be due to high temperature and large velocity dispersion. The large velocity dispersion is probably caused by large external pressure and tidal forces. (C)1999 COSPAR. Published by Elsevier Science Ltd.
  • K Sorai, N Nakai, N Kuno, K Nishiyama  CENTRAL REGIONS OF THE GALAXY AND GALAXIES  141  -142  1998  [Not refereed][Not invited]
  • T Hasegawa, J Morino, T Sawada, T Handa, K Sato, T Oka, S Sakamoto, K Sorai, M Seta, M Hayashi, L Bronfman, J May, R Booth, LA Nyman, P Shaver  CENTRAL REGIONS OF THE GALAXY AND GALAXIES  179  -180  1998  [Not refereed][Not invited]
  • N Kuno, N Nakai, K Nishiyama, K Sorai, T Handa, T Iga  CENTRAL REGIONS OF THE GALAXY AND GALAXIES  243  -244  1998  [Not refereed][Not invited]
  • Kazuo Sorai, Kohta Nishiyama, Tetsuo Hasegawa, Takeshi Miyaji, Nobuharu Ukita  Nobeyama Radio Observatory Technical Report  (60)  1  -10  1998  [Not refereed][Not invited]
  • T Hasegawa, J Morino, T Sawada, T Handa, K Sato, T Oka, S Sakamoto, K Sorai, M Seta, M Hayashi, L Bronfman, J May, R Booth, LA Nyman, P Shaver  CENTRAL REGIONS OF THE GALAXY AND GALAXIES  179  -180  1998  [Not refereed][Not invited]
  • N Kuno, N Nakai, K Nishiyama, K Sorai, T Handa, T Iga  CENTRAL REGIONS OF THE GALAXY AND GALAXIES  243  -244  1998  [Not refereed][Not invited]
  • Kazuo Sorai, Kohta Nishiyama, Tetsuo Hasegawa, Takeshi Miyaji, Nobuharu Ukita  Nobeyama Radio Observatory Technical Report  (60)  1  -10  1998  [Not refereed][Not invited]
  • T Hasegawa, JI Morino, K Sorai, T Handa, K Sato, T Oka, M Seta, S Sakamoto, M Hayashi, R Booth, LA Nyman, L Bronfman, M Rubio, P Shaver  DIFFUSE INFRARED RADIATION AND THE IRTS  124-  244  -250  1997  [Not refereed][Not invited]
     
    First results of the wide-angle survey of the CO J=2-1 line emission from the southern sky are reported. The observations were made with a dedicated 60-cm radio telescope at La Silla, Chile, and the data are directly compared with the Columbia survey of the CO J=1-0 emission. In the fourth quadrant of the Milky Way, the Norma and Centaurus arms show higher 2-1/1-0 line intensity ratios, while the 3-kpc expanding arm shows markedly lower ratios. The overall distribution of the ratio in the Galactic disk can be expressed as a superposition of these irregularities on the galactic-scale gradient of the ratio decreasing with the galactocentric radius. Giant molecular clouds in the Large Magellanic Cloud (LMC) exhibit CO 2-1/1-0 ratios ranging from 0.5 to 1.3, similar to those in the Milky Way. The ratio does not correlate well with the indicators of massive star formation in the recent past. Combined with the concentration of high ratio gas in spiral arms noted in the Milky Way, this supports the hypothesis that the high CO 2-1/1-0 ratio highlights dense concentrations of molecular gas ready for massive star formation. The 30 Dor molecular cloud complex contains a large amount of high ratio gas. Among the other clouds, we found a tendency that higher ratios are observed for clouds closer to the kinetic center of the LMC. Some global mechanism may control the physical conditions of molecular gas there.
  • 12CO (J = 2-1) emission in the inner galaxy
    Kazuo Sorai, Tetsuo Hasegawa, Toshihiro Handa, Seiichi Sakamoto, Tomoharu Oka, Masamichi Seta, Kumiko Sato, Jun Ichi Morino, Masahiko Hayashi, Hiroko Shinnaga  IAU Symposium No.170, CO:Twenty-five Years of Millimeter-wave Spectroscopy  463  1997  [Not refereed][Not invited]
  • A 12CO(J=2-1)Survey of the First Quadrant of the Galaxy
    Kazuo Sorai, Seiichi Sakamoto, Tetsuo hasegawa, Toshihiro Handa, Masahiko hayashi, Tomoharu Oka, Masumichi Seta, Kumiko Sato, Sato Hiroko Shinnagam, Jun Ichi Morino  Proceedings of Third East-Asian Meeting on Astronomy, Ground-Based Astronomu in Asia, edited by Norio Kaifu  115  -120  1996  [Not refereed][Not invited]

Association Memberships

  • International Astronomical Union   日本天文学会   the Astronomical Society of Japan   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2020/04 -2023/03 
    Author : 徂徠 和夫
     
    本研究は，銀河内部において恒星の材料となる星間ガスの質量を空間分解した上で正確に測定し，星生成率，ガス質量，星質量の間の関係を定量化することを目的とする．研究は，１）近傍銀河内部の領域ごとの高精度な分子ガス質量の導出，２）近傍銀河内部の領域ごとの原子ガス質量及び暗黒ガスの質量の導出，３）星質量-星生成率-ガス質量の関係の定量化と大局的な星生成過程の解明，という３つの観点から進める計画で，初年度は１）に着手した． 近傍銀河を空間分解し領域ごとに複数の方法で精度良く分子ガスの質量を求めるための基本となる一酸化炭素分子の複数のスペクトル線の撮像データは，既に私たちが国立天文台野辺山宇宙電波観測所45 m電波望遠鏡で取得した147銀河のデータである．対象を増やすために同望遠鏡の共同利用観測に新たに22天体の観測提案を行い採択され，このうち11天体の観測を実施，現在解析中である． 私たちの観測では，一酸化炭素分子の回転量子数が１から０に遷移するスペクトル線（１２C１６Oと同位体の１３C１６O）を取得しているが，これと異なる遷移のスペクトル線（１２C１６Oの回転量子数が２から１及び３から２へ遷移するもの）のデータは，海外の望遠鏡で取得されアーカイブされているものを利用した．私たちのサンプルと比較可能な共通の銀河合計１３天体について，これら４本のスペクトル線データを銀河の中心から同心円環に分けてデータをスタックし，励起計算を試みた結果，分子ガスの単純な一層モデルでは正確な励起状態を得ることが困難なことが明らかになった． また，一酸化炭素のスペクトル線強度から水素分子を主成分とする分子ガス全体の総量を推定する「変換係数」が金属量依存することから，銀河内部の金属量を測定する観測を兵庫県立大学西はりま天文台なゆた望遠鏡の共同利用観測で実施し，２天体についてデータが得られた．解析はこれからである．
  • Kinematics and Star Formation in the Galaxy
    Date (from‐to) : 2001 -2008
  • Molecular Gas and Star Formation in Barred Spiral Galaxies
    Cooperative Research
    Date (from‐to) : 2003 -2004
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2002 -2004 
    Author : HABE Asao, FUJIMOTO Msayuki, KANEKO Noboru, NAKAI Naomasa, KAMENO Seiji, SORAI Kazuo
     
    In order to upgrade Hokkaido University 11m radio telescope, we have made the new radio receiver of 22Ghz, the hone for 22GHz receiver, the degital spctrum analyzers, and the control system of Hokkaido university 11m radio telescope. Purpose of our study is to investigate of property of global star formation in our galaxy, by observation of Anmonia molecules whic is in dense cores in molecular clouds in our galaxy. In this study, we will observe four, different spectral lines from highly exitation of rotational states of Anmonia molecules to know rotational excitation temperature, since study of density and temperature is very important to study star formation in molecular clouds. We have made the test observation of Anmonia molecules in the Cygnus region which is in the spiral arm in our Galaxy. We have succeeded to detect (J,K)=(1,1),(2,2) and (3,3)lines. By using the intensity of these lines, we deduce temperature of molecules which is 20K and is consistent with previous observation. We will make survey observation of Anmolia molecules in dense molecular clouds in our galaxy to study global star formation.

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