Tanaka, Kunihiko



Faculty of Science and Technology, Department of Physics (Yagami)


Research Associate/Assistant Professor/Instructor

External Links

Career 【 Display / hide

  • 2005.04

    University of Tokyo, Institute of Astronomy

  • 2008.04

    National Astronomical Observatory Japan, Nobeyama Radio Observatory, PD


Research Areas 【 Display / hide

  • Natural Science / Astronomy

Research Keywords 【 Display / hide

  • Radio Astronomy

Research Themes 【 Display / hide

  • 銀河系中心、大質量星形成、近傍銀河, 


     View Summary

    Galactic Center, Massive Star Formation, Nearby Galaxies


Papers 【 Display / hide

  • Distributions of the Density and Kinetic Temperature of the Molecular Gas in the Central Region of NGC 613 Using Hierarchical Bayesian Inference

    Kaneko, Hiroyuki; Tosaki, Tomoka; Tanaka, Kunihiko ; Miyamoto, Yusuke

    The Astrophysical Journal (IOP publishing)  953   139 2023.08

    Research paper (scientific journal), Joint Work, Accepted

  • Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI

    Huang, K. -Y. ; Viti, S. ; Holdship, J. ; Mangum, J. G. ; Martín, S. ; Harada, N. ; Muller, S. ; Sakamoto, K. ; Tanaka, K. ; Yoshimura, Y. ; Herrero-Illana, R. ; Meier, D. S. ; Behrens, E. ; van der Werf, P. P. ; Henkel, C. ; García-Burillo, S. ; Rivilla, V. M. ; Emig, K. L. ; Colzi, L. search by orcid ; Humire, P. K. ; ...


    Research paper (scientific journal), Joint Work, Accepted

  • Volume Density Structure of the NGC253 CMZ through ALCHEMI Excitation Analysis

    Tanaka, Kunihiko ; Mangum, Jeffrey G. ; Viti, Serena ; Martin, Sergio ; Harada, Nanase ; Sakamoto, Kazushi ; Muller, Sebastien ; Yoshimura, Yuki ; Nakanishi, Kouichiro ; Herrero Illana, Ruben ; Emig, Kimberly L. ; Muhle, S. ; Kaneko, Hiroyuki ; Tosaki, Tomoka ; Behrens, Erica ; Rivilla, Victor M. ; Colzi, Laura ; Nishimura, Yuri ; Humire, P. K. ; Bouvier, Mathilde ; Huang, Ko-Yun ; Butterworth, Joshua ; Meier, David S. ; van der Werf, Paul P.

    The Astrophysical Journal (IOP publishing)   2023

    Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted

  • Energizing Star Formation: The Cosmic-Ray Ionization Rate in NGC 253 Derived from ALCHEMI Measurements of H<inf>3</inf>O<sup>+</sup>and SO

    Holdship J., Mangum J.G., Viti S., Behrens E., Harada N., Martín S., Sakamoto K., Muller S., Tanaka K., Nakanishi K., Herrero-Illana R., Yoshimura Y., Aladro R., Colzi L., Emig K.L., Henkel C., Nishimura Y., Rivilla V.M., Van Der Werf P.P.

    Astrophysical Journal (Astrophysical Journal)  931 ( 2 )  2022.06

    Research paper (scientific journal), Accepted,  ISSN  0004637X

     View Summary

    The cosmic-ray ionization rate (CRIR) is a key parameter in understanding the physical and chemical processes in the interstellar medium. Cosmic rays are a significant source of energy in star formation regions, impacting the physical and chemical processes that drive the formation of stars. Previous studies of the circum-molecular zone of the starburst galaxy NGC 253 have found evidence for a high CRIR value: 103-106 times the average CRIR within the Milky Way. This is a broad constraint, and one goal of this study is to determine this value with much higher precision. We exploit ALMA observations toward the central molecular zone of NGC 253 to measure the CRIR. We first demonstrate that the abundance ratio of H3O+ and SO is strongly sensitive to the CRIR. We then combine chemical and radiative transfer models with nested sampling to infer the gas properties and CRIR of several star-forming regions in NGC 253 from emission from their transitions. We find that each of the four regions modeled has a CRIR in the range (1-80) × 10-14 s-1 and that this result adequately fits the abundances of other species that are believed to be sensitive to cosmic rays, including C2H, HCO+, HOC+, and CO. From shock and photon-dominated/X-ray dominated region models, we further find that neither UV-/X-ray-driven nor shock-dominated chemistry is a viable single alternative as none of these processes can adequately fit the abundances of all of these species.

  • First extragalactic detection of a phosphorus-bearing molecule with ALCHEMI: Phosphorus nitride (PN)

    Haasler, D. search by orcid ; Rivilla, V. M. ; Martín, S. ; Holdship, J. ; Viti, S. ; Harada, N. ; Mangum, J. ; Sakamoto, K. ; Muller, S. ; Tanaka, K. ; Yoshimura, Y. ; Nakanishi, K. ; Colzi, L. search by orcid ; Hunt, L. search by orcid ; Emig, K. L. ; Aladro, R. ; Humire, P. ; Henkel, C. ; van der Werf, P.

    Astronomy & Astrophysics (Astronomy and Astrophysics)  659   158 2022.03

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  00046361

     View Summary

    Context. Phosphorus (P) is a crucial element for life given its central role in several biomolecules. P-bearing molecules have been discovered in different regions of the Milky Way, but not yet towards an extragalactic environment. Aims. We searched for P-bearing molecules outside the Milky Way towards the nearby starburst Galaxy NGC 253. Methods. Using observations from the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) project, we used the MAdrid Data CUBe Analysis package to model the emission of P-bearing molecules assuming local thermodynamic equilibrium (LTE) conditions. We also performed a non-LTE analysis using SpectralRadex. Results. We report the detection of a P-bearing molecule, phosphorus nitride (PN), for the first time in an extragalactic environment, towards two giant molecular clouds (GMCs) of NGC 253. The LTE analysis yields total PN beam-averaged column densities N = (1.20 ± 0.09) - 1013 cm-2 and N = (6.5 ± 1.6) - 1012 cm-2, which translate into abundances with respect to H2 of = (8.0 ± 1.0) - 10-12 and = (4.4 ± 1.2) - 10-12. We derived a low excitation temperature of Tex = (4.4 ± 1.3) K towards the GMC with the brightest PN emission, which indicates that PN is sub-thermally excited. The non-LTE analysis results in column densities consistent with the LTE values. We also searched for other P-bearing molecules (PO, PH3, CP, and CCP), and upper limits were derived. The derived PO/PN ratios are < 1.3 and < 1.7. The abundance ratio between PN and the shock-tracer SiO derived towards NGC 253 follows the same trend previously found towards Galactic sources. Conclusions. Comparison of the observations with chemical models indicates that the derived molecular abundances of PN in NGC 253 can be explained by shock-driven chemistry followed by cosmic-ray-driven photochemistry.

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Papers, etc., Registered in KOARA 【 Display / hide

Presentations 【 Display / hide

  • Star Formation Conditions In the Milky Way’s Galactic Central Molecular Zone

    TANAKA Kunihiko

    Star Formation in Different Environments 2017, 


  • Search for the CO-dark Mass in the Central Molecular Zone by using the ASTE 10-m Telescope

    TANAKA Kunihiko

    IAUS 322: The Multi-Messenger Astrophysics of the Galactic Centre, 


    Oral presentation (general)

  • CO-0.30-0.07: A Candidate Site of Collision-induced Massive Star Formation in the Milky Way's Central Molecular Zon

    TANAKA Kunihiko

    The 6th Zermatt ISM Symposium",, 


    Oral presentation (general)

  • Giant Molecular Clouds with High Abundance of Atomic Carbon and Cyano Radical in the Milky Way's Central Molecular Zone

    TANAKA Kunihiko

    IAU General Assembly, Meeting #29 (Honolulu, HA, USA) , 


    Poster presentation, International Astronomical Union

  • The ASTE Galactic Center Survey in the 350 and 500 GHz Bands

    TANAKA Kunihiko

    New Trends in Radio Astronomy in the ALMA Era / the 30th Anniversary of Nobeyama Radio Observatory (Hakone, Kanagawa, Japan) , 


    Oral presentation (general)

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Research Projects of Competitive Funds, etc. 【 Display / hide

  • 銀河系中心領域での局所的な爆発的星形成現象


    日本学術振興会, Grant-in-Aid for Scientific Research, Research grant, Principal investigator

  • ミリ波-サブミリ波観測で探る銀河系中心活動性


    日本学術振興会, Grant-in-Aid for Scientific Research, Research grant, Principal investigator

Works 【 Display / hide

  • 夏の星空から始める天文学:銀河系中心の不思議な天体たち






Courses Taught 【 Display / hide











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Memberships in Academic Societies 【 Display / hide

  • Astronomical Society Japan