Updated on 2024/02/06

写真a

 
Muraoka Kazuyuki
 
Organization
Graduate School of Science Department of Physics Associate Professor
School of Science Department of Physics
Title
Associate Professor
Affiliation
Institute of Science
Affiliation campus
Nakamozu Campus

Position

  • Graduate School of Science Department of Physics 

    Associate Professor  2022.04 - Now

  • School of Science Department of Physics 

    Associate Professor  2022.04 - Now

Degree

  • 博士(理学) ( Others ) (   The University of Tokyo )

Research Areas

  • Natural Science / Astronomy  / Astronomy

  • Natural Science / Astronomy

Research Interests

  • Interstellar Physics

  • Galactic Astronomy

  • Radio Astronomy

  • nearby galaxies

  • star formation

  • radio Astronomy

Research subject summary

  • ミリ波サブミリ波帯ヘテロダイン受信機の開発

  • 近傍銀河における星間物質と星形成の観測的研究

Research Career

  • Radio Astronomy

    molecular gas, submillimeter wave, star formation, galaxies  Joint Research in Japan

    2009.10 - Now 

Professional Memberships

  • International Astronomical Union

    2012.01 - Now   Overseas

  • ASJ

    2003.04 - Now   Domestic

  • THE ASTRONOMICAL SOCIETY OF JAPAN

  • 国際天文学連合

Committee Memberships (off-campus)

  • 欧文研究報告 編集委員   日本天文学会  

    2023.06 - Now 

Job Career (off-campus)

  • Osaka Prefecture University   Graduate School of Science, Department of Physical Science

    2017.10 - Now

Papers

  • ACA CO( J = 2-1) Mapping of the Nearest Spiral Galaxy M33. I. Initial Results and Identification of Molecular Clouds Reviewed

    Muraoka K.

    Astrophysical Journal   953 ( 2 )   2023.08( ISSN:0004637X

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   Kind of work:Joint Work   International / domestic magazine:International journal  

    DOI: 10.3847/1538-4357/ace4bd

  • CO multi-line imaging of nearby galaxies (COMING). XII. CO-to-H2 conversion factor and dust-to-gas ratio Reviewed

    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   75 ( 4 )   743 - 786   2023.06( ISSN:00046264

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    DOI: 10.1093/pasj/psad034

  • Diverse Molecular Structures across the Whole Star-forming Disk of M83: High-fidelity Imaging at 40 pc Resolution Reviewed

    Jin Koda, Akihiko Hirota, Fumi Egusa, Kazushi Sakamoto, Tsuyoshi Sawada, Mark Heyer, Junichi Baba, Samuel Boissier, Daniela Calzetti, Jennifer Donovan Meyer, Bruce G. Elmegreen, Armando Gil de Paz, Nanase Harada, Luis C. Ho, Masato I. N. Kobayashi, Nario Kuno, Amanda M Lee, Barry F. Madore, Fumiya Maeda, Sergio Martín, Kazuyuki Muraoka, Kouichiro Nakanishi, Sachiko Onodera, Jorge L. Pineda, Nick Scoville, Yoshimasa Watanabe

    The Astrophysical Journal   949 ( 2 )   108 - 108   2023.06( ISSN:0004-637X

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    Abstract

    We present Atacama Large Millimeter/submillimeter Array (ALMA) imaging of molecular gas across the full star-forming disk of the barred spiral galaxy M83 in CO(J = 1–0). We jointly deconvolve the data from ALMA’s 12 m, 7 m, and Total Power arrays using the MIRIAD package. The data have a mass sensitivity and resolution of 10<sup>4</sup>M<sub>⊙</sub> (3σ) and 40 pc—sufficient to detect and resolve a typical molecular cloud in the Milky Way with a mass and diameter of 4 × 10<sup>5</sup>M<sub>⊙</sub> and 40 pc, respectively. The full disk coverage shows that the characteristics of molecular gas change radially from the center to outer disk, with the locally measured brightness temperature, velocity dispersion, and integrated intensity (surface density) decreasing outward. The molecular gas distribution shows coherent large-scale structures in the inner part, including the central concentration, offset ridges along the bar, and prominent molecular spiral arms. However, while the arms are still present in the outer disk, they appear less spatially coherent, and even flocculent. Massive filamentary gas concentrations are abundant even in the interarm regions. Building up these structures in the interarm regions would require a very long time (≳100 Myr). Instead, they must have formed within stellar spiral arms and been released into the interarm regions. For such structures to survive through the dynamical processes, the lifetimes of these structures and their constituent molecules and molecular clouds must be long (≳100 Myr). These interarm structures host little or no star formation traced by Hα. The new map also shows extended CO emission, which likely represents an ensemble of unresolved molecular clouds.

    DOI: 10.3847/1538-4357/acc65e

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/acc65e/pdf

  • An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. II. CO Cloud Catalog Reviewed

    Takahiro Ohno, Kazuki Tokuda, Ayu Konishi, Takeru Matsumoto, Marta Sewiło, Hiroshi Kondo, Hidetoshi Sano, Kisetsu Tsuge, Sarolta Zahorecz, Nao Goto, Naslim Neelamkodan, Tony Wong, Hajime Fukushima, Tatsuya Takekoshi, Kazuyuki Muraoka, Akiko Kawamura, Kengo Tachihara, Yasuo Fukui, Toshikazu Onishi

    The Astrophysical Journal   949 ( 2 )   63 - 63   2023.05( ISSN:0004-637X

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    Abstract

    The nature of molecular clouds and their statistical behavior in subsolar metallicity environments are not fully explored yet. We analyzed data from an unbiased CO (J = 2–1) survey at the spatial resolution of ∼2 pc in the northern region of the Small Magellanic Cloud with the Atacama Compact Array to characterize the CO cloud properties. A cloud-decomposition analysis identified 426 spatially/velocity-independent CO clouds and their substructures. Based on the cross-matching with known infrared catalogs by Spitzer and Herschel, more than 90% CO clouds show spatial correlations with point sources. We investigated the basic properties of the CO clouds and found that the radius–velocity linewidth (R–σ<sub>v</sub>) relation follows the Milky Way-like power-law exponent, but the intercept is ∼1.5 times lower than that in the Milky Way. The mass functions (dN/dM) of the CO luminosity and virial mass are characterized by an exponent of ∼1.7, which is consistent with previously reported values in the Large Magellanic Cloud and in the Milky Way.

    DOI: 10.3847/1538-4357/accadb

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/accadb/pdf

  • Discovery of a Giant Molecular Loop in the Central Region of NGC 253 Reviewed

    R. Konishi, R. Enokiya, Y. Fukui, K. Muraoka, K. Tokuda, T. Onishi

    The Astrophysical Journal   929 ( 1 )   63 - 63   2022.04( ISSN:0004-637X

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    Abstract

    NGC 253 is a starburst galaxy of SAB(s)c type with increasing interest because of its high activity at unrivaled closeness. Its energetic event is manifested as the vertical gas features in its central molecular zone, for which stellar feedback was proposed as the driving engine. In order to pursue details of the activity, we have undertaken a kinematic analysis of the ALMA archive data of <sup>12</sup>CO(J = 3 − 2) emission at the highest resolution ∼3 pc. We revealed that one of the non-rotating gas components in the central molecular zone shows a loop-like structure of ∼200 pc radius. The loop-like structure is associated with a star cluster, whereas the cluster is not inside the loop-like structure and is not likely as the driver of the loop-like structure formation. Further, we find that the bar potential of NGC 253 seems to be too weak to drive the gas motion by the eccentric orbit. As an alternative, we frame a scenario that magnetic acceleration by the Parker instability is responsible for the creation of the loop-like structure. We show that the observed loop-like structure properties are similar to those in the Milky Way, and argue that recent magneto-hydrodynamics simulations lend support for the picture having the magnetic field strength of ≳100 μG. We suggest that cluster formation was triggered by the falling gas to the footpoint of the loop, which is consistent with a typical dynamical timescale of the loop ∼1 Myr.

    DOI: 10.3847/1538-4357/ac58f7

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/ac58f7/pdf

  • An Unbiased CO Survey toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. I. Overview: CO Cloud Distributions Reviewed

    Kazuki Tokuda, Hiroshi Kondo, Takahiro Ohno, Ayu Konishi, Hidetoshi Sano, Kisetsu Tsuge, Sarolta Zahorecz, Nao Goto, Naslim Neelamkodan, Tony Wong, Marta Sewiło, Hajime Fukushima, Tatsuya Takekoshi, Kazuyuki Muraoka, Akiko Kawamura, Kengo Tachihara, Yasuo Fukui, Toshikazu Onishi

    The Astrophysical Journal   922 ( 2 )   171 - 171   2021.12( ISSN:0004-637X

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    Abstract

    We have analyzed the data from a large-scale CO survey toward the northern region of the Small Magellanic Cloud (SMC) obtained with the Atacama Compact Array (ACA) stand-alone mode of ALMA. The primary aim of this study is to comprehensively understand the behavior of CO as an H<sub>2</sub> tracer in a low-metallicity environment (Z ∼ 0.2 Z<sub>⊙</sub>). The total number of mosaic fields is ∼8000, which results in a field coverage of 0.26 deg<sup>2</sup> (∼2.9 ×10<sup>5</sup> pc<sup>2</sup>), corresponding to ∼10% of the area of the galaxy. The sensitive ∼2 pc resolution observations reveal the detailed structure of the molecular clouds previously detected in the single-dish NANTEN survey. We have detected a number of compact CO clouds within lower H<sub>2</sub> column density (∼10<sup>20</sup> cm<sup>−2</sup>) regions whose angular scale is similar to the ACA beam size. Most of the clouds in this survey also show peak brightness temperature as low as &lt;1 K, which for optically thick CO emission implies an emission size much smaller than the beam size, leading to beam dilution. The comparison between an available estimation of the total molecular material traced by thermal dust emission and the present CO survey demonstrates that more than ∼90% of H<sub>2</sub> gas cannot be traced by the low-J CO emission. Our processed data cubes and 2D images are publicly available.

    DOI: 10.3847/1538-4357/ac1ff4

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/ac1ff4/pdf

  • ALMA Observations of Giant Molecular Clouds in M33. III. Spatially Resolved Features of the Star formation Inactive Million-solar-mass Cloud Reviewed

    Hiroshi Kondo, Kazuki Tokuda, Kazuyuki Muraoka, Atsushi Nishimura, Shinji Fujita, Tomoka Tosaki, Sarolta Zahorecz, Rie E. Miura, Masato I. N. Kobayashi, Sachiko Onodera, Kazufumi Torii, Nario Kuno, Hidetoshi Sano, Toshikazu Onishi, Kazuya Saigo, Yasuo Fukui, Akiko Kawamura, Kisetsu Tsuge, Kengo Tachihara

    The Astrophysical Journal   912 ( 1 )   66 - 66   2021.05( ISSN:0004-637X

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    DOI: 10.3847/1538-4357/abeb65

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/abeb65/pdf

  • CO Multi-line Imaging of Nearby Galaxies (COMING). IX. 12CO(J = 2–1)/12CO(J = 1–0) line ratio on kiloparsec scales Reviewed

    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   2021.04( ISSN:0004-6264

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    <title>Abstract</title>
    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).

    DOI: 10.1093/pasj/psaa119

  • Current status and future plan of Osaka Prefecture University 1.85-m mm-submm telescope project

    Atsushi Nishimura, Kazuki Tokuda, Ryohei Harada, Yutaka Hasegawa, Shota Ueda, Sho Masui, Ryotaro Konishi, Yasumasa Yamasaki, Hiroshi Kondo, Koki Yokoyama, Takeru Matsumoto, Taisei Minami, Masanari Okawa, Shinji Fujita, Ayu Konishi, Yuka Nakao, Shimpei Nishimoto, Sana Kawashita, Sho Yoneyama, Tatsuyuki Takashima, Kenta Goto, Nozomi Okada, Kimihiro Kimura, Yasuhiro Abe, Kazuyuki Muraoka, Hiroyuki Maezawa, Toshikazu Onishi, Hideo Ogawa

    Ground-based and Airborne Telescopes VIII   2020.12

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    Publishing type:Research paper (international conference proceedings)  

    DOI: 10.1117/12.2560955

  • ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star Formation by Multiple Gas Colliding Events at the NGC 604 Complex Reviewed

    Kazuyuki Muraoka, Hiroshi Kondo, Kazuki Tokuda, Atsushi Nishimura, Rie E. Miura, Sachiko Onodera, Nario Kuno, Sarolta Zahorecz, Kisetsu Tsuge, Hidetoshi Sano, Shinji Fujita, Toshikazu Onishi, Kazuya Saigo, Kengo Tachihara, Yasuo Fukui, Akiko Kawamura

    The Astrophysical Journal   903 ( 2 )   94 - 94   2020.11

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/abb822

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/abb822

  • CO Multi-line Imaging of Nearby Galaxies (COMING). X. Physical conditions of molecular gas and the local SFR–mass relation Reviewed

    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 )   90   2020.10( ISSN:0004-6264

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    <title>Abstract</title>
    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.

    DOI: 10.1093/pasj/psaa084

  • ALMA Observations of Giant Molecular Clouds in M33 I: Resolving Star Formation Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock Reviewed

    Kazuki Tokuda, Kazuyuki Muraoka, Hiroshi Kondo, Atsushi Nishimura, Tomoka Tosaki, Sarolta Zahorecz, Sachiko Onodera, Rie E. Miura, Kazufumi Torii, Nario Kuno, Shinji Fujita, Hidetoshi Sano, Toshikazu Onishi, Kazuya Saigo, Yasuo Fukui, Akiko Kawamura, Kengo Tachihara

    Astrophysical Journal   893 ( 1 )   36 - 36   2020.06

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    We report molecular line and continuum observations toward one of the most<br />
    massive giant molecular clouds (GMCs), GMC-16, in M33 using ALMA with an<br />
    angular resolution of 0\farcs44 $\times$ 0\farcs27 ($\sim$2 pc $\times$ 1 pc).<br />
    We have found that the GMC is composed of several filamentary structures in<br />
    $^{12}$CO and $^{13}$CO ($J$ = 2--1). The typical length, width, and total mass<br />
    are $\sim$50--70 pc, $\sim$5--6 pc, and $\sim$10$^{5}$ $M_{\odot}$,<br />
    respectively, which are consistent with those of giant molecular filaments<br />
    (GMFs) as seen in the Galactic GMCs. The elongations of the GMFs are roughly<br />
    perpendicular to the direction of the galaxy&#039;s rotation, and several H$\;${\sc<br />
    ii} regions are located at the downstream side relative to the filaments with<br />
    an offset of $\sim$10--20 pc. These observational results indicate that the<br />
    GMFs are considered to be produced by a galactic spiral shock. The 1.3 mm<br />
    continuum and C$^{18}$O ($J$ = 2--1) observations detected a dense clump with<br />
    the size of $\sim$2 pc at the intersection of several filamentary clouds, which<br />
    is referred to as $&quot;$hub-filament.$&quot;$ The first example of protostellar outflow<br />
    in M33 also has been identified at the center of the clump. We have<br />
    successfully resolved the pc-scale local star formation activity in which the<br />
    galactic scale kinematics may induce the formation of the parental filamentary<br />
    clouds.

    DOI: 10.3847/1538-4357/ab8ad3

  • Systematic Variations of CO J = 2−1/1–0 Ratio and Their Implications in The Nearby Barred Spiral Galaxy M83 Reviewed

    Jin Koda, Tsuyoshi Sawada, Kazushi Sakamoto, Akihiko Hirota, Fumi Egusa, Samuel Boissier, Daniela Calzetti, Jennifer Donovan Meyer, Bruce G. Elmegreen, Armando Gil de Paz, Nanase Harada, Luis C. Ho, Masato I. N. Kobayashi, Nario Kuno, Sergio Martín, Kazuyuki Muraoka, Kouichiro Nakanishi, Nick Scoville, Mark Seibert, Catherine Vlahakis, Yoshimasa Watanabe

    The Astrophysical Journal   890 ( 1 )   L10 - L10   2020.02

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    Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/2041-8213/ab70b7

    Other URL: https://iopscience.iop.org/article/10.3847/2041-8213/ab70b7

  • 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 Reviewed

    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 ( 6 )   S13   2019.12( ISSN:0004-6264

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    <title>Abstract</title>We present the results of $^{12}\textrm{C}$$\textrm{O}$(J = 1–0) and $^{13}\textrm{C}$$\textrm{O}$(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 $\textrm{C}$$\textrm{O}$ data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of $^{12}\textrm{C}$$\textrm{O}$ to $^{13}\textrm{C}$$\textrm{O}$ (R12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, $n(\rm {H_2})$ 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 $n(\rm {H}_2)$ on the velocity dispersion of inter-molecular clouds (ΔV/sin i). Specifically, n(H2) increases as ΔV/sin i increases when ΔV/sin i &amp;lt; 100 km s−1. On the other hand, n(H2) decreases as ΔV/sin i increases when ΔV/sin i &amp;gt; 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.

    DOI: 10.1093/pasj/psz022

  • CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency Reviewed

    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 ( 6 )   S15   2019.12( ISSN:0004-6264

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    Authorship:Lead author, Corresponding author   Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    <title>Abstract</title>
    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 &amp;lt; 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.

    DOI: 10.1093/pasj/psz015

  • CO multi-line imaging of nearby galaxies (COMING). IV. Overview of the project Reviewed

    Kazuo Sorai, Nario Kuno, Kazuyuki Muraoka, Yusuke Miyamoto, Hiroyuki Kaneko, Hiroyuki Nakanishi, Naomasa Nakai, Kazuki Yanagitani, Takahiro Tanaka, Yuya Sato, Dragan Salak, Michiko Umei, Kana Morokuma-Matsui, Naoko Matsumoto, Saeko Ueno, Hsi-An Pan, Yuto Noma, Tsutomu T Takeuchi, Moe Yoda, Mayu Kuroda, Atsushi Yasuda, Yoshiyuki Yajima, Nagisa Oi, Shugo Shibata, Masumichi Seta, Yoshimasa Watanabe, Shoichiro Kita, Ryusei Komatsuzaki, Ayumi Kajikawa, Yu Yashima, Suchetha Cooray, Hiroyuki Baji, Yoko Segawa, Takami Tashiro, Miho Takeda, Nozomi Kishida, Takuya Hatakeyama, Yuto Tomiyasu, Chey Saita

    Publications of the Astronomical Society of Japan   71 ( 6 )   S14   2019.11( ISSN:0004-6264

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    Publishing type:Research paper (scientific journal)  

    <title>Abstract</title>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.

    DOI: 10.1093/pasj/psz115

  • ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions Reviewed

    Hidetoshi Sano, Kisetsu Tsuge, Kazuki Tokuda, Kazuyuki Muraoka, Kengo Tachihara, Yumiko Yamane, Mikito Kohno, Shinji Fujita, Rei Enokiya, Gavin Rowell, Nigel Maxted, Miroslav D. Filipovic, Jonathan Knies, Manami Sasaki, Toshikazu Onishi, Paul P. Plucinsky, Yasuo Fukui

    Publications of the Astronomical Society of Japan   2019.08

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    We report the first evidence for high-mass star formation triggered by<br />
    collisions of molecular clouds in M33. Using the Atacama Large<br />
    Millimeter/submillimeter Array, we spatially resolved filamentary structures of<br />
    giant molecular cloud 37 in M33 using $^{12}$CO($J$ = 2-1), $^{13}$CO($J$ =<br />
    2-1), and C$^{18}$O($J$ = 2-1) line emission at a spatial resolution of $\sim$2<br />
    pc. There are two individual molecular clouds with a systematic velocity<br />
    difference of $\sim$6 km s$^{-1}$. Three continuum sources representing up to<br />
    $\sim$10 high-mass stars with the spectral types of B0V-O7.5V are embedded<br />
    within the densest parts of molecular clouds bright in the C$^{18}$O($J$ = 2-1)<br />
    line emission. The two molecular clouds show a complementary spatial<br />
    distribution with a spatial displacement of $\sim$3.5 pc, and show a V-shaped<br />
    structure in the position-velocity diagram. These observational features traced<br />
    by CO and its isotopes are consistent with those in high-mass star-forming<br />
    regions created by cloud-cloud collisions in the Galactic and Magellanic Cloud<br />
    HII regions. Our new finding in M33 indicates that the cloud-cloud collision is<br />
    a promising process to trigger high-mass star formation in the Local Group.

  • Discovery of Shocked Molecular Clouds Associated with the Shell-type Supernova Remnant RX J0046.5−7308 in the Small Magellanic Cloud Reviewed

    H. Sano, H. Matsumura, Y. Yamane, P. Maggi, K. Fujii, K. Tsuge, K. Tokuda, R. Z. E. Alsaberi, M. D. Filipović, N. Maxted, G. Rowell, H. Uchida, T. Tanaka, K. Muraoka, T. Takekoshi, T. Onishi, A. Kawamura, T. Minamidani, N. Mizuno, H. Yamamoto, K. Tachihara, T. Inoue, S. Inutsuka, F. Voisin, N. F. H. Tothill, M. Sasaki, N. M. McClure-Griffiths, Y. Fukui

    The Astrophysical Journal   881 ( 1 )   85 - 85   2019.08

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    Publishing type:Research paper (scientific journal)   International / domestic magazine:International journal  

    DOI: 10.3847/1538-4357/ab2ade

    Other URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab2ade

  • CO Multi-line Imaging of Nearby Galaxies (COMING). VII. Fourier decomposition of molecular gas velocity fields and bar pattern speed Reviewed

    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   71 ( 6 )   S16   2019.02( ISSN:0004-6264

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    Publishing type:Research paper (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≡ RCRab approx 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.

    DOI: 10.1093/pasj/psz004

  • ALMA 12CO (J=1-0) imaging of the nearby galaxy M 83: Variations in the efficiency of star formation in giant molecular clouds Reviewed

    Akihiko Hirota, Fumi Egusa, Jun'ichi Baba, Nario Kuno, Kazuyuki Muraoka, Tomoka Tosaki, Rie Miura, Hiroyuki Nakanishi, Ryohei Kawabe

    Publications of the Astronomical Society of Japan 雑誌 日本天文学会   70 ( 4 )   2018.08

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    Kind of work:Joint Work  

  • ALMA observations of N83C in the early stage of star formation in the Small Magellanic Cloud Reviewed

    Kazuyuki Muraoka, Aya Homma, Toshikazu Onishi, Kazuki Tokuda, Ryohei Harada, Yuuki Morioka, Sarolta Zahorecz, Kazuya Saigo, Akiko Kawamura, Norikazu Mizuno, Tetsuhiro Minamidani, Erik Muller, Yasuo Fukui, Margaret Meixner, Remy Indebetouw, Marta Sewilo, Alberto Bolatto

    Astrophysical Journal 雑誌 American Astronomical Society   844 ( 2 )   2017.08

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    Kind of work:Joint Work  

  • Kennicutt-Schmidt Relation Variety and Star-forming Cloud Fraction Reviewed

    Kana Morokuma-Matsui, Kazuyuki Muraoka

    Astrophysical Journal 雑誌 American Astronomical Society   837 ( 2 )   2017.03

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    Kind of work:Joint Work  

  • CO Multi-line Imaging of Nearby Galaxies (COMING). I. Physical properties of molecular gas in the barred spiral galaxy NGC 2903 Reviewed

    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

    Publication of the Astronomical Society of Japan 雑誌 Astronomical Society of Japan   68 ( 5 )   2016.10

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    Kind of work:Joint Work  

  • CO(J=3-2) on-the-fly mapping of the nearby spiral galaxies NGC 628 and NGC 7793: Spatially resolved CO(J=3-2) star-formation law Reviewed

    Kazuyuki Muraoka, Miho Takeda, Kazuki Yanagitani, Hiroyuki Kaneko, Kouichiro Nakanishi, Nario Kuno, Kazuo Sorai, Tomoka Tosaki, Kotaro Kohno

    Publication of the Astronomical Society of Japan Astronomical Society of Japan   68 ( 2 )   2016.04

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    Kind of work:Joint Work  

  • 13CO(J=1-0) On-the-Fly Mapping of the Giant HII region NGC 604: Variation in Molecular Gas Density and Temperature due to Sequential Star Formation Reviewed

    Kazuyuki Muraoka, Tomoka Tosaki, Rie Miura, Sachiko Onodera, Nario Kuno, Kouichiro Nakanishi, Hiroyuki Kaneko, Shinya Komugi

    Publication of the Astronomical Society of Japan Astronomical Society of Japan   64 ( 1 )   2012.02

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    Kind of work:Joint Work  

  • ASTE CO(3-2) Mapping toward the Whole Optical Disk of M 83: Properties of Inter-arm Giant Molecular-cloud Associations Reviewed

    Kazuyuki Muraoka, Kotaro Kohno, Tomoka Tosaki, Nario Kuno, Kouichiro Nakanishi, Kazuo Sorai, Tsuyoshi Sawada, Kunihiko Tanaka, Toshihiro Handa, Masayuki Fukuhara, Hajime Ezawa, Ryohei Kawabe

    Astrophysical Journal IOP science   706   1213 - 1225   2009.12

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Books and Other Publications

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  • Demonstration of Experiments in Physics II

    2021   Practical Training  

  • Introduction to Life, Environment, and Advanced Sciences

    2021    

  • Fundamental Experimental Physics

    2021   Practical Training  

  • Astronomy A

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  • Electricity & Magnetism II

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  • Astrophysics I

    2021    

  • Astrophysics II

    2021    

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    2021    

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Charge of off-campus class subject

  • 電磁気学II

    Institution:Osaka Prefecture University

  • 物理科学専門実験

    Institution:Osaka Prefecture University

  • 物理科学実験

    Institution:Osaka Prefecture University

  • 情報基礎BI

    Institution:Osaka Prefecture University

  • 宇宙物理学特論I

    Institution:Osaka Prefecture University

  • 宇宙物理学A

    Institution:Osaka Prefecture University

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Social Activities

  • 堺市立堺高等学校 プロフェッサーズセミナー 目に見えない宇宙を見る~電波天文学の紹介~

    2018.04 - 2019.03

  • 日本物理学会 大阪支部公開シンポジウム 世界の果ての千里眼—究極の電波干渉計アルマ(ALMA)が切り拓く、最新の天文学—

    2013.04 - 2014.03

  • 第6回 サイエンスコミュニケーションカフェ 世界の果てから、宇宙をあばく~究極の電波望遠鏡:ALMA、間もなく始動~

    2010.04 - 2011.03