Sorai Kazuo

Faculty of Science　Physics　Nonlinear PhysicsProfessor
Last Updated :2025/12/04

■Researcher basic information

Degree

  • Doctor(Science), The University of Tokyo

Researchmap personal page

Home Page URL

J-Global ID

Research Keyword

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

Research Field

  • Natural sciences, Astronomy

Educational Organization

■Career

Career

  • Apr. 2021 - Present
    Hokkaido University, Faculty of Science, Professor
  • Oct. 2021 - Mar. 2024
    University of Tsukuba, Faculty of Pure and Applied Sciences, Professor (cross appointment)
  • Apr. 2017 - Sep. 2021
    University of Tsukuba, Faculty of Pure and Applied Sciences, Associate Professor (cross appointment)
  • Apr. 2012 - Mar. 2021
    Hokkaido University, Faculty of Science, Associate Professor
  • Apr. 2007 - Mar. 2012
    Hokkaido University, Faculty of Science, Assistant Professor
  • Apr. 2006 - Mar. 2007
    Hokkaido University, Faculty School of Science, Research Associate
  • May 2002 - Mar. 2006
    Hokkaido University, Graduate School of Science, Research Associate

■Research activity information

Papers

  • CO multi-line imaging of nearby galaxies (COMING). XII. CO-to-H2 conversion factor and dust-to-gas ratio
    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, 10 Jun. 2023, [Peer-reviewed]
    Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). IX. 12CO(J = 2–1)/12CO(J = 1–0) line ratio on kiloparsec scales
    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, Oxford University Press (OUP), 05 Apr. 2021, [Peer-reviewed]
    Scientific journal, 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).
  • The molecular mass function of the local Universe
    P. Andreani, Y. Miyamoto, H. Kaneko, A. Boselli, K. Tatematsu, K. Sorai, R. Vio
    Astronomy & Astrophysics, 643, L11, L11, EDP Sciences, Nov. 2020, [Peer-reviewed]
    Scientific journal, 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.
  • Molecular Gas Outflow in the Starburst Galaxy NGC 1482
    Dragan Salak, Naomasa Nakai, Kazuo Sorai, Yusuke Miyamoto
    The Astrophysical Journal, 05 Oct. 2020, [Peer-reviewed]
    Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). X. Physical conditions of molecular gas and the local SFR–mass relation
    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, Oxford University Press (OUP), 02 Oct. 2020, [Peer-reviewed]
    Scientific journal, 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.
  • A method for unmasking incomplete astronomical signals: Application to the CO Multi-line Imaging of Nearby Galaxies project
    Suchetha Cooray, Tsutomu T. Takeuchi, Moe Yoda, Kazuo Sorai
    Publications of the Astronomical Society of Japan, 72, 4, Oxford University Press, 01 Aug. 2020, [Peer-reviewed]
    English, Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency
    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, Dec. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303
    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, Dec. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • CO Multi-line Imaging of Nearby Galaxies (COMING). VII. Fourier decomposition of molecular gas velocity fields and bar pattern speed
    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, Dec. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • CO multi-line imaging of nearby galaxies (COMING). IV. Overview of the project
    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, Dec. 2019, [Peer-reviewed], [Lead author]
    Scientific journal, 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....
  • CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303
    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, Dec. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency
    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, Dec. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • The Galactic center lobe filled with thermal plasma
    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, Aug. 2019, [Peer-reviewed]
    English, Scientific journal
  • A 3 mm Spectral Line Survey toward the Barred Spiral Galaxy NGC 3627
    Watanabe, Yoshimasa, Nishimura, Yuri, Sorai, Kazuo, Sakai, Nami, Kuno, Nario, Yamamoto, Satoshi
    The Astrophysical Journal Supplement Series, 242, 26, Jun. 2019, [Peer-reviewed]
    English, Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303
    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, Oxford University Press (OUP), Mar. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency
    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, Oxford University Press (OUP), Mar. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • The Excitation State of Galactic Diffuse Molecular Gas, Investigated with ALMA Observations of Multi-transition Absorption Lines
    Ryo Ando, Kotaro Kohno, Hideki Umehata, Takuma Izumi, Shun Ishii, Yuri Nishimura, Kazuo Sorai, Tomoka Tosaki, Akio Taniguchi, Yoichi Tamura
    The Astrophysical Journal, 05 Feb. 2019, [Peer-reviewed]
    Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). VII. Fourier decomposition of molecular gas velocity fields and bar pattern speed
    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, Oxford University Press (OUP), Feb. 2019, [Peer-reviewed]
    Scientific journal, 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....
  • The Dust-selected Molecular Clouds in the Northeast Region of the Small Magellanic Cloud
    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, 06 Nov. 2018, [Peer-reviewed]
    English, Scientific journal
  • The Dust-Selected Molecular Clouds in the Northeast Region of the Small Magellanic Cloud
    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, Sep. 2018, [Peer-reviewed]
    English, Scientific journal
  • 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, Jul. 2018, [Peer-reviewed]
    English, Scientific journal
  • Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images
    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, American Astronomical Society, 06 Nov. 2017, [Peer-reviewed]
    English, Scientific journal
  • 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, Nov. 2017, [Peer-reviewed]
    English, Scientific journal
  • OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSSJ110006.07+442144.3
    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, Oct. 2017, [Peer-reviewed]
    English, Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). II. Transitions between atomic and molecular gas, diffuse and dense gas, gas and stars in the dwarf galaxy NGC2976
    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, Aug. 2017, [Peer-reviewed]
    English, Scientific journal
  • A face-on accretion system in high mass star-formation: Possible dusty infall streams within 100 astronomical unit
    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, Cambridge University Press, 2017
    English, Scientific journal
  • THE 1.1 mm CONTINUUM SURVEY OF THE SMALL MAGELLANIC CLOUD: PHYSICAL PROPERTIES AND EVOLUTION OF THE DUST-SELECTED CLOUDS
    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, Jan. 2017, [Peer-reviewed]
    English, Scientific journal
  • Accelerating a water maser face-on jet from a high mass young stellar object
    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, Oct. 2016, [Peer-reviewed]
    English, Scientific journal
  • Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. II. Internal proper motion measurement in G006.79-00.25
    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, Oct. 2016, [Peer-reviewed]
    English, Scientific journal
  • The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy
    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, Oct. 2016, [Peer-reviewed]
    English, Scientific journal
  • CO Multi-line Imaging of Nearby Galaxies (COMING). I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903
    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, Oct. 2016, [Peer-reviewed]
    English, Scientific journal
  • CO(J=3-2) on-the-fly mapping of the nearby spiral galaxies NGC628 and NGC7793: Spatially resolved CO(J=3-2) star-formation law
    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, Apr. 2016, [Peer-reviewed]
    English, Scientific journal
  • Search for molecular gas in XUV disk of M83
    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, Cambridge University Press ({CUP}), Mar. 2016, [Peer-reviewed]
    Scientific journal
  • MOLECULAR DISTRIBUTION IN THE SPIRAL ARM OF M51
    Yoshimasa Watanabe, Nami Sakai, Kazuo Sorai, Junko Ueda, Satoshi Yamamoto
    ASTROPHYSICAL JOURNAL, 819, 2, 144:1, 144:11, Mar. 2016, [Peer-reviewed]
    English, Scientific journal
  • Development of the New Multi-Beam 100 GHz Band SIS Receiver FOREST for the Nobeyama 45-m Telescope
    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, 2016, [Peer-reviewed]
    English, International conference proceedings
  • MOLECULAR GAS AND STAR-FORMATION PROPERTIES IN THE CENTRAL AND BAR REGIONS OF NGC 6946
    Hsi-An Pan, Nario Kuno, Jin Koda, Akihiko Hirota, Kazuo Sorai, Hiroyuki Kaneko
    ASTROPHYSICAL JOURNAL, 815, 1, 59:1, 59:14, Dec. 2015, [Peer-reviewed]
    English, Scientific journal
  • Constraints on the minor merging and star formation history of the Wolf-Rayet galaxy NGC5430 through observations
    Hsi-An Pan, Nario Kuno, Kazuo Sorai, Michiko Umei
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 67, 6, 116:1, 116:17, Dec. 2015, [Peer-reviewed]
    English, Scientific journal
  • CO emissions from optically selected galaxies at z similar to 0.1-0.2: Tight anti-correlation between molecular gas fraction and 4000 angstrom break strength
    Kana Morokuma-Matsui, Junichi Baba, Kazuo Sorai, Nario Kuno
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 67, 3, 36:1, 36:13, Jun. 2015, [Peer-reviewed]
    English, Scientific journal
  • Stacking analysis of (CO)-C-12 and (CO)-C-13 spectra of NGC3627: Existence of non-optically thick (CO)-C-12 emission?
    Kana Morokuma-Matsui, Kazuo Sorai, Yoshimasa Watanabe, Nario Kuno
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 67, 1, Feb. 2015, [Peer-reviewed]
    English, Scientific journal
  • CO Emissions from Optically Selected Galaxies at z similar to 0.1-0.2: Tight Anti-Correlation Between Molecular Gas Fraction and 4000 Angstrom Break Strength
    Kana Morokuma-Matsui, Junichi Baba, Kazuo Sorai, Nario Kuno
    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR, 499, 157, 158, 2015, [Peer-reviewed]
    English, International conference proceedings
  • Spectral Line Survey Toward Spiral Arm of M51
    Watanabe Yoshimasa, Sakai Nami, Sorai Kazuo, Nishimura Yuri, Yamamoto Satoshi
    REVOLUTION IN ASTRONOMY WITH ALMA: THE THIRD YEAR, 499, 151, 152, 2015, [Peer-reviewed]
  • Ionized Gas Observation Toward a Nearby Starburst Galaxy NGC 253
    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, [Peer-reviewed]
  • Stacking analysis of <sup>12</sup>CO and <sup>13</sup>CO spectra of NGC3627: Existence of non-optically thick <sup>12</sup>CO emission?
    Kana Morokuma-Matsui, Kazuo Sorai, Yoshimasa Watanabe, Nario Kuno
    Publications of the Astronomical Society of Japan, 67, 1, 2:1, 2:17, Oxford University Press, 2015, [Peer-reviewed]
    English, Scientific journal
  • VLBI observations of bright AGN jets with the KVN and VERA Array (KaVA): Evaluation of imaging capability
    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, Dec. 2014, [Peer-reviewed]
    English, Scientific journal
  • SPECTRAL LINE SURVEY TOWARD THE SPIRAL ARM OF M51 IN THE 3 AND 2 mm BANDS
    Yoshimasa Watanabe, Nami Sakai, Kazuo Sorai, Satoshi Yamamoto
    ASTROPHYSICAL JOURNAL, 788, 1, 4:1, 4:20, Jun. 2014, [Peer-reviewed]
    English, Scientific journal
  • Observations of 6.7 GHz methanol masers with East-Asian VLBI Network. I. VLBI images of the first epoch of observations
    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, Apr. 2014, [Peer-reviewed]
    English, Scientific journal
  • Gas accretion history of galaxies at z ∼ 0 - 2: Comparison of the observational data of molecular gas with the mass evolution model of galaxies
    Kana Morokuma, Junichi Baba, Kazuo Sorai, Nario Kuno
    Proceedings of the International Astronomical Union, 10, 332, Cambridge University Press, 2014, [Peer-reviewed]
    English, International conference proceedings
  • Development of Nayoro Optical Camera and Spectrograph for 1.6-m Pirka telescope of Hokkaido University
    Hikaru Nakao, Makoto Watanabe, Kazuo Sorai, Mahiro Yamada, Yoichi Itoh, Shigeyuki Sako, Takashi Miyata
    GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 9147, 91473P, 2014
    English, International conference proceedings
  • 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, Oct. 2013, [Peer-reviewed]
    English, International conference proceedings
  • Detection of an ultra-bright submillimeter galaxy behind the Small Magellanic Cloud
    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, 29 Aug. 2013, [Peer-reviewed]
    English, Scientific journal, 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.
  • The GENJI Programme: Gamma-Ray Emitting Notable AGN Monitoring by Japanese VLBI
    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, Apr. 2013, [Peer-reviewed]
    English, Scientific journal
  • Nuclear radio jet from a low-luminosity active galactic nucleus in NGC 4258
    Akihiro Doi, Kotaro Kohno, Kouichiro Nakanishi, Seiji Kameno, Makoto Inoue, Kazuhiro Hada, Kazuo Sorai
    Astrophysical Journal, 765, 1, 63:1, 63:11, Institute of Physics Publishing, 01 Mar. 2013, [Peer-reviewed]
    English, Scientific journal
  • Dense cloud formation and star formation in a barred galaxy
    M. Nimori, A. Habe, K. Sorai, Y. Watanabe, A. Hirota, D. Namekata
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 429, 3, 2175, 2182, Mar. 2013, [Peer-reviewed]
    English, Scientific journal
  • Development of 32-m Radio Telescopes for Monitoring Observations of Methanol Masers, H2O Masers, and Radio Continuum
    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, [Peer-reviewed]
    English, International conference proceedings
  • High Gas Fraction of Barred Spiral Galaxies at z similar to 0.1-0.2
    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, [Peer-reviewed]
    English, International conference proceedings
  • Intermittent maser flare around the high-mass young stellar object G353.273+0.641 - II. Detection of a radio and molecular jet
    K. Motogi, K. Sorai, K. Niinuma, K. Sugiyama, M. Honma, K. Fujisawa
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 428, 1, 349, 353, Jan. 2013, [Peer-reviewed]
    English, Scientific journal
  • PHYSICAL CONDITIONS IN MOLECULAR CLOUDS IN THE ARM AND INTERARM REGIONS OF M51
    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, Dec. 2012, [Peer-reviewed]
    English, Scientific journal
  • Optics Design and Optimizations of the Multi-Color TES Bolometer Camera for the ASTE Telescope
    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, Nov. 2012, [Peer-reviewed]
    English, Scientific journal
  • 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, Oct. 2012
    English, International conference proceedings
  • Formation of Dense Gas and Stars near the End of the Galactic Bar
    Ohishi Yukie, Sorai Kazuo, Habe Asao
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 64, 4, "74, 1"-"74-11", 25 Aug. 2012, [Peer-reviewed]
    English
  • Intermittent maser flare around the high-mass young stellar object G353.273+0.641
    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, Jul. 2012
    English, International conference proceedings
  • Properties of molecular gas in the bar of maffei 2
    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, Jun. 2012, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Detection of CO(J = 1-0) emission from barred spiral galaxies at z ∼ 0.1
    Matsui K, Sorai K, Watanabe Y, Kuno N
    Publications of the Astronomical Society of Japan, 64, 55, Jun. 2012, [Peer-reviewed]
    English, Scientific journal
  • NH3 Survey Observation of Massive Star-Forming Region W 43
    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, 64, 2, 30, 1"-"30-17", Astronomical Society of Japan, Apr. 2012, [Peer-reviewed]
    English, Scientific journal, 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.
  • Optics design of the multi-color TES bolometer camera for the ASTE telescope
    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
    International conference proceedings
  • Giant Molecular Clouds in the Spiral Arm of IC 342
    Akihiko Hirota, Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Kazuo Sorai
    AStrophysical Journal Letters, 737, 1, 40, Nov. 2011, [Peer-reviewed]
    Scientific journal
  • Intermittent maser flare around the high-mass young stellar object G353.273+0.641 - I. Data and overview
    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, Oct. 2011, [Peer-reviewed]
    English, Scientific journal
  • 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, 01 Mar. 2011, [Peer-reviewed]
    English, Scientific journal
  • Refined molecular gas mass and star-formation efficiency in NGC3627
    Watanabe Y, Sorai K, Kuno N, Habe A
    Monthly Notices of the Royal Astronomical Society, 411, 3, 1409, 1417, Mar. 2011, [Peer-reviewed]
    English, Scientific journal
  • New Distance and Revised Natures of High-Mass Star Formation in G5.89－0.39
    Motogi K, Sorai K, Habe A, Honma M
    PASJ, 63, 1, 31, 44, Astronomical Society of Japan, 2011, [Peer-reviewed]
    English
  • Variation of Molecular Gas Properties Across the Spiral Arms in IC 342: Large-Scale (CO)-C-13 (1-0) Emission
    Akihiko Hrota, Nario Kuno, Naoko Sato, Hiroyuki Nakanishi, Tomoka Tosaki, Kazuo Sorai
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN, 62, 5, 1261, 1275, Oct. 2010, [Peer-reviewed]
    English, Scientific journal
  • VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars
    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, Oxford University Press (OUP), 25 Dec. 2009, [Peer-reviewed]
    Scientific journal
  • ASTE CO (3-2) MAPPING TOWARD THE WHOLE OPTICAL DISK OF M 83: PROPERTIES OF INTER-ARM GIANT MOLECULAR-CLOUD ASSOCIATIONS
    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, American Astronomical Society, 10 Nov. 2009, [Peer-reviewed]
    Scientific journal
  • Determination of the Pattern Speed of Barred Spiral Galaxies
    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, Oxford University Press (OUP), 25 Jun. 2009, [Peer-reviewed]
    Scientific journal
  • Nobeyama Millimeter Array Observations of the Nuclear Starburst of M 83: A GMA Scale Correlation between Dense Gas Fraction and Star Formation Efficiency
    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, Oxford University Press (OUP), 25 Apr. 2009, [Peer-reviewed]
    Scientific journal
  • Large-Scale NH3Observations toward the Galactic Star-Forming Regions I. W 51 Molecular Cloud Complex
    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, Oxford University Press (OUP), 25 Dec. 2008, [Peer-reviewed], [Lead author]
    Scientific journal
  • Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars
    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, Oxford University Press (OUP), 25 Oct. 2008, [Peer-reviewed]
    Scientific journal
  • H2O Maser Outflow from the Red Supergiant Star NML Cygni Observed with Japanese VLBI Network
    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, Oxford University Press (OUP), 25 Oct. 2008, [Peer-reviewed]
    Scientific journal
  • Microstructure and kinematics of H2O masers in the massive star-forming region IRAS 06061+2151
    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, Oxford University Press (OUP), Sep. 2008, [Peer-reviewed]
    Scientific journal
  • Central Spiral Structure of Molecular Gas in Maffei 2
    Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Toshihito Shibatsuka
    Publications of the Astronomical Society of Japan, 60, 3, 475, 485, Oxford University Press (OUP), 25 Jun. 2008, [Peer-reviewed]
    Scientific journal
  • ASTE CO(3-2) Observations of the Southern Barred Spiral Galaxy NGC 986: a Large Gaseous Bar Filled with a Dense Molecular Medium
    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, Oxford University Press (OUP), 25 Jun. 2008, [Peer-reviewed]
    Scientific journal
  • GMCs in the nearby galaxy IC 342
    Akihiko Hirota, N. Kuno, N. Sato, T. Tosaki, H. Nakanishi, K. Sorai
    MAPPING THE GALAXY AND NEARBY GALAXIES, 334, 334, 2008, [Peer-reviewed]
    English, International conference proceedings
  • Nobeyama CO atlas of nearby spiral galaxies
    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, +, 2008, [Peer-reviewed]
    English, International conference proceedings
  • CO(3-2) wide area imaging of M 83 with ASTE: Correlation between CO(3-2)/CO(1-0) ratios and star formation efficiencies
    Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Seiichi Sakamoto
    MAPPING THE GALAXY AND NEARBY GALAXIES, 357, 357, 2008, [Peer-reviewed]
    English, International conference proceedings
  • Kinematics of molecular gas in the bar of Maffei 2
    Sorai Kazuo, Kuno Nario, Nakai Naomasa, Matsui Hidenori, Habe Asao
    MAPPING THE GALAXY AND NEARBY GALAXIES, 380, 2008, [Peer-reviewed]
  • Japanese VLBI Network Observations of Radio-Loud Narrow-Line Seyfert 1 Galaxies
    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, Oxford University Press (OUP), 25 Aug. 2007, [Peer-reviewed]
    Scientific journal
  • A collimated jet and an infalling-rotating disk in G192 traced by H2O maser emission
    Hiroshi Imai, Toshihiro Omodaka, Tomoya Hirota, Tomofumi Umemoto, Kazuo Sorai, Tetsuro Kondo
    Proceedings of the International Astronomical Union, 3, 242, 340, 341, Mar. 2007, [Peer-reviewed]
    English, International conference proceedings
  • Nobeyama CO Atlas of Nearby Spiral Galaxies: Distribution of Molecular Gas in Barred and Nonbarred Spiral Galaxies
    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, Oxford University Press (OUP), 25 Feb. 2007, [Peer-reviewed]
    Scientific journal
  • ASTE CO (3–2) Observations of the Barred Spiral Galaxy M 83: I. Correlation between CO (3–2)/CO (1–0) Ratios and Star Formation Efficiencies
    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, Oxford University Press (OUP), 25 Feb. 2007, [Peer-reviewed]
    Scientific journal
  • Central structure of molecular gas in maffei 2
    Nario Kuno, Koichiro Nakanishi, Kazuo Sorai, Toshihito Shibatsuka
    Astrophysics and Space Science Proceedings, 202409, 379, 382, Springer Netherlands, 2007, [Peer-reviewed]
    English, International conference proceedings
  • ASTE observations of dense molecular gas in galaxies
    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
    English, International conference proceedings
  • Environmental Effects on Gaseous Disks of the Virgo Spiral Galaxies
    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, American Astronomical Society, 10 Nov. 2006, [Peer-reviewed]
    Scientific journal
  • A Collimated Jet and an Infalling-Rotating Disk in G192.16−3.84 Traced by H2O Maser Emission
    Hiroshi Imai, Toshihiro Omodaka, Tomoya Hirota, Tomofumi Umemoto, Kazuo Sorai, Tetsuro Kondo
    Publications of the Astronomical Society of Japan, 58, 5, 883, 892, Oxford University Press (OUP), 25 Oct. 2006, [Peer-reviewed]
    Scientific journal
  • ASTE CO(3-2) observations of M 83: Correlation between CO(3-2)/CO(1-0) ratios and star formation efficiencies
    K. Muraoka, K. Kohno, T. Tosaki, N. Kuno, K. Nakanishi, K. Sorai, S. Sakamoto
    Proceedings of the International Astronomical Union, 2, 237, 451, Aug. 2006, [Peer-reviewed]
    English, International conference proceedings
  • Distribution of molecular gas in barred spiral galaxies
    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, Aug. 2006, [Peer-reviewed]
    English, International conference proceedings
  • Water-Vapor Maser Survey for Active Galactic Nuclei: A Megamaser in NGC 6926
    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, Oxford University Press (OUP), 25 Aug. 2005, [Peer-reviewed]
    Scientific journal
  • Dense Molecular Gas in Lenticular Galaxies
    Nario Kuno, Naomasa Nakai, Kazuo Sorai, Kohta Nishiyama, Baltasar Vila-VilarÓ
    Publications of the Astronomical Society of Japan, 54, 4, 555, 560, Oxford University Press (OUP), 25 Aug. 2002, [Peer-reviewed]
    Scientific journal
  • Radial Distributions of the HCN/CO Ratio in Nearby CO Bright Galaxies
    Kazuo Sorai, Naomasa Nakai, Nario Kuno, Kohta Nishiyama
    Publications of the Astronomical Society of Japan, 54, 2, 179, 194, Oxford University Press (OUP), 25 Apr. 2002, [Peer-reviewed], [Lead author]
    Scientific journal
  • A Large-Scale CO Mapping of the Central Region of W 51
    Shin-ichiro Okumura, Ryosuke Miyawaki, Kazuo Sorai, Takuya Yamashita, Tetsuo Hasegawa
    Publications of the Astronomical Society of Japan, 53, 5, 793, 798, Oxford University Press (OUP), 25 Oct. 2001, [Peer-reviewed]
    Scientific journal
  • The Tokyo‐Onsala‐ESO‐Calan Galactic CO J  = 2–1 Survey. I. The Galactic Center Region
    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, American Astronomical Society, Sep. 2001, [Peer-reviewed]
    Scientific journal
  • The COJ = 2–1 / J = 1–0 Ratio in the Large Magellanic Cloud
    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, American Astronomical Society, 20 Apr. 2001, [Peer-reviewed], [Lead author]
    Scientific journal
  • Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. II. NGC 253
    Kazuo Sorai, Naomasa Nakai, Nario Kuno, Kohta Nishiyama, Tetsuo Hasegawa
    Publications of the Astronomical Society of Japan, 52, 5, 785, 802, Oxford University Press (OUP), 01 Oct. 2000, [Peer-reviewed], [Lead author]
    Scientific journal
  • Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. I. NGC 3504
    Nario Kuno, Kohta Nishiyama, Naomasa Nakai, Kazuo Sorai, Baltasar Vila-Vilaró, Toshihiro Handa
    Publications of the Astronomical Society of Japan, 52, 5, 775, 783, Oxford University Press (OUP), 01 Oct. 2000, [Peer-reviewed]
    Scientific journal
  • Enhanced COJ= 2–1/J= 1–0 Ratio as a Marker of Supernova Remnant–Molecular Cloud Interactions: The Cases of W44 and IC 443
    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, American Astronomical Society, 20 Sep. 1998, [Peer-reviewed]
    Scientific journal
  • An Isotope Study of Carbon Monoxide in the Edge‐on Galaxy NGC 891
    Seiichi Sakamoto, Toshihiro Handa, Yoshiaki Sofue, Mareki Honma, Kazuo Sorai
    The Astrophysical Journal, 475, 1, 134, 143, American Astronomical Society, 20 Jan. 1997, [Peer-reviewed]
    Scientific journal

Other Activities and Achievements

Courses

  • 物理学I　　　　　　　　　　　　　　　
    北海道大学

Affiliated academic society

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

Research Themes

  • Study of star formation in galaxies based on precise measurement of mass of interstellar gas
    Grants-in-Aid for Scientific Research
    Apr. 2020 - Mar. 2023
    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．
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, Principal investigator, 20K04008
  • Kinematics and Star Formation in the Galaxy　　　　　　　　　　　　　　　
    2001 - 2008
    Competitive research funding
  • Molecular Gas and Star Formation in Barred Spiral Galaxies　　　　　　　　　　　　　　　
    Cooperative Research
    2003 - 2004
    Competitive research funding
  • Study of Global Star formation in Our Galaxy by servey observation of Emission lines of Anmonia molecules
    Grants-in-Aid for Scientific Research
    2002 - 2004
    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.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 14340058