Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis
We present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing...
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad0e64 |
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| author | Kunihiko Tanaka Jeffrey G. Mangum Serena Viti Sergio Martín Nanase Harada Kazushi Sakamoto Sebastien Muller Yuki Yoshimura Kouichiro Nakanishi Rubén Herrero-Illana Kimberly L. Emig S. Mühle Hiroyuki Kaneko Tomoka Tosaki Erica Behrens Víctor M. Rivilla Laura Colzi Yuri Nishimura P. K. Humire Mathilde Bouvier Ko-Yun Huang Joshua Butterworth David S. Meier Paul P. van der Werf |
| author_facet | Kunihiko Tanaka Jeffrey G. Mangum Serena Viti Sergio Martín Nanase Harada Kazushi Sakamoto Sebastien Muller Yuki Yoshimura Kouichiro Nakanishi Rubén Herrero-Illana Kimberly L. Emig S. Mühle Hiroyuki Kaneko Tomoka Tosaki Erica Behrens Víctor M. Rivilla Laura Colzi Yuri Nishimura P. K. Humire Mathilde Bouvier Ko-Yun Huang Joshua Butterworth David S. Meier Paul P. van der Werf |
| author_sort | Kunihiko Tanaka |
| collection | DOAJ |
| description | We present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing NGC 253 from the quiescent Milky Way’s Galactic center (GC). Non-LTE analyses employing a hierarchical Bayesian framework are applied to Band 3–7 transitions from nine molecular species to delineate the position–position–velocity distributions of column density ( ${N}_{{{\rm{H}}}_{2}}$ ), volume density ( ${n}_{{{\rm{H}}}_{2}}$ ), and temperature ( T _kin ) at 27 pc resolution. Two distinct components are detected: a low-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\sim ({10}^{3.3}\ {\mathrm{cm}}^{-3},85\ {\rm{K}})$ and a high-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\,\sim ({10}^{4.4}\ {\mathrm{cm}}^{-3},110\ {\rm{K}})$ , separated at ${n}_{{{\rm{H}}}_{2}}\sim {10}^{3.8}\ {\mathrm{cm}}^{-3}$ . NGC 253 has ∼10 times the high-density gas mass and ∼3 times the dense-gas mass fraction of the GC. These properties are consistent with their HCN/CO ratio but cannot alone explain the factor of ∼30 difference in their star formation efficiencies (SFEs), contradicting the dense-gas mass to star formation rate scaling law. The ${n}_{{{\rm{H}}}_{2}}$ histogram toward NGC 253 exhibits a shallow declining slope up to ${n}_{{{\rm{H}}}_{2}}\sim {10}^{6}\ {\mathrm{cm}}^{-3}$ , while that of the GC steeply drops in ${n}_{{{\rm{H}}}_{2}}\gtrsim {10}^{4.5}\ {\mathrm{cm}}^{-3}$ and vanishes at 10 ^5 cm ^−3 . Their dense-gas mass fraction ratio becomes consistent with their SFEs when the threshold ${n}_{{{\rm{H}}}_{2}}$ for the dense gas is taken at ∼10 ^4.2−4.6 cm ^−3 . The rich abundance of gas above this density range in the NGC 253 CMZ, or its scarcity in the GC, is likely to be the critical difference characterizing the contrasting star formation in the centers of the two galaxies. |
| first_indexed | 2024-03-08T14:46:18Z |
| format | Article |
| id | doaj.art-bf869a7ddf2443dbb7ec505bc43cc298 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T14:46:18Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-bf869a7ddf2443dbb7ec505bc43cc2982024-01-11T09:50:18ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0196111810.3847/1538-4357/ad0e64Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation AnalysisKunihiko Tanaka0https://orcid.org/0000-0001-8153-1986Jeffrey G. Mangum1https://orcid.org/0000-0003-1183-9293Serena Viti2https://orcid.org/0000-0001-8504-8844Sergio Martín3https://orcid.org/0000-0001-9281-2919Nanase Harada4https://orcid.org/0000-0002-6824-6627Kazushi Sakamoto5https://orcid.org/0000-0001-5187-2288Sebastien Muller6https://orcid.org/0000-0002-9931-1313Yuki Yoshimura7https://orcid.org/0000-0002-1413-1963Kouichiro Nakanishi8https://orcid.org/0000-0002-6939-0372Rubén Herrero-Illana9https://orcid.org/0000-0002-7758-8717Kimberly L. Emig10https://orcid.org/0000-0001-6527-6954S. Mühle11Hiroyuki Kaneko12https://orcid.org/0000-0002-2699-4862Tomoka Tosaki13https://orcid.org/0000-0001-9016-2641Erica Behrens14https://orcid.org/0000-0002-2333-5474Víctor M. Rivilla15https://orcid.org/0000-0002-2887-5859Laura Colzi16https://orcid.org/0000-0001-8064-6394Yuri Nishimura17https://orcid.org/0000-0003-0563-067XP. K. Humire18https://orcid.org/0000-0003-3537-4849Mathilde Bouvier19https://orcid.org/0000-0003-0167-0746Ko-Yun Huang20https://orcid.org/0000-0002-1227-8435Joshua Butterworth21https://orcid.org/0000-0002-5353-1775David S. Meier22https://orcid.org/0000-0001-9436-9471Paul P. van der Werf23https://orcid.org/0000-0001-5434-5942Department of Physics, Faculty of Science and Technology, Keio University , 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522, Japan ; ktanaka@phys.keio.ac.jpNational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903-2475, USALeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The Netherlands; Department of Physics and Astronomy, University College London , Gower Street, London WC1E6BT, UKEuropean Southern Observatory , Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile; Joint ALMA Observatory , Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, ChileNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Institute of Astronomy and Astrophysics , Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI) , 2-21-1 Osawa, Mitaka, Tokyo 181-1855, JapanInstitute of Astronomy and Astrophysics , Academia Sinica, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Road, Taipei 10617, TaiwanDepartment of Space, Earth and Environment, Chalmers University of Technology , Onsala Space Observatory, SE-43992 Onsala, SwedenInstitute of Astronomy, Graduate School of Science, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, JapanNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI) , 2-21-1 Osawa, Mitaka, Tokyo 181-1855, JapanEuropean Southern Observatory , Alonso de Córdova, 3107, Vitacura, Santiago 763-0355, Chile; Institute of Space Sciences (ICE, CSIC) , Campus UAB, Carrer de Magrans, E-08193 Barcelona, SpainNational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903-2475, USAArgelander-Institut für Astronomie, Universität Bonn , Auf dem Hügel 71, D-53121 Bonn, GermanyInstitute of Science and Technology, Niigata University , 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan; Joetsu University of Education , 1, Yamayashiki-machi, Joetsu, Niigata 943-8512, JapanJoetsu University of Education , 1, Yamayashiki-machi, Joetsu, Niigata 943-8512, JapanDepartment of Astronomy, University of Virginia , P.O. Box 400325, 530 McCormick Road, Charlottesville, VA 22904-4325, USACentro de Astrobiología (CSIC-INTA) , Ctra. de Ajalvir Km. 4, Torrejón de Ardoz, E-28850 Madrid, Spain; INAF-Osservatorio Astrofisico di Arcetri , Largo Enrico Fermi 5, I-50125, Florence, ItalyCentro de Astrobiología (CSIC-INTA) , Ctra. de Ajalvir Km. 4, Torrejón de Ardoz, E-28850 Madrid, SpainNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Institute of Astronomy, Graduate School of Science, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, JapanMax-Planck-Institut für Radioastronomie , Auf dem Hügel 69, D-53121 Bonn, GermanyLeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The NetherlandsLeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The NetherlandsLeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The NetherlandsNew Mexico Institute of Mining and Technology , 801 Leroy Place, Socorro, NM 87801, USA; National Radio Astronomy Observatory , P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801, USALeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The NetherlandsWe present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing NGC 253 from the quiescent Milky Way’s Galactic center (GC). Non-LTE analyses employing a hierarchical Bayesian framework are applied to Band 3–7 transitions from nine molecular species to delineate the position–position–velocity distributions of column density ( ${N}_{{{\rm{H}}}_{2}}$ ), volume density ( ${n}_{{{\rm{H}}}_{2}}$ ), and temperature ( T _kin ) at 27 pc resolution. Two distinct components are detected: a low-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\sim ({10}^{3.3}\ {\mathrm{cm}}^{-3},85\ {\rm{K}})$ and a high-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\,\sim ({10}^{4.4}\ {\mathrm{cm}}^{-3},110\ {\rm{K}})$ , separated at ${n}_{{{\rm{H}}}_{2}}\sim {10}^{3.8}\ {\mathrm{cm}}^{-3}$ . NGC 253 has ∼10 times the high-density gas mass and ∼3 times the dense-gas mass fraction of the GC. These properties are consistent with their HCN/CO ratio but cannot alone explain the factor of ∼30 difference in their star formation efficiencies (SFEs), contradicting the dense-gas mass to star formation rate scaling law. The ${n}_{{{\rm{H}}}_{2}}$ histogram toward NGC 253 exhibits a shallow declining slope up to ${n}_{{{\rm{H}}}_{2}}\sim {10}^{6}\ {\mathrm{cm}}^{-3}$ , while that of the GC steeply drops in ${n}_{{{\rm{H}}}_{2}}\gtrsim {10}^{4.5}\ {\mathrm{cm}}^{-3}$ and vanishes at 10 ^5 cm ^−3 . Their dense-gas mass fraction ratio becomes consistent with their SFEs when the threshold ${n}_{{{\rm{H}}}_{2}}$ for the dense gas is taken at ∼10 ^4.2−4.6 cm ^−3 . The rich abundance of gas above this density range in the NGC 253 CMZ, or its scarcity in the GC, is likely to be the critical difference characterizing the contrasting star formation in the centers of the two galaxies.https://doi.org/10.3847/1538-4357/ad0e64Star formationGiant molecular cloudsStarburst galaxiesGalactic centerInterstellar medium |
| spellingShingle | Kunihiko Tanaka Jeffrey G. Mangum Serena Viti Sergio Martín Nanase Harada Kazushi Sakamoto Sebastien Muller Yuki Yoshimura Kouichiro Nakanishi Rubén Herrero-Illana Kimberly L. Emig S. Mühle Hiroyuki Kaneko Tomoka Tosaki Erica Behrens Víctor M. Rivilla Laura Colzi Yuri Nishimura P. K. Humire Mathilde Bouvier Ko-Yun Huang Joshua Butterworth David S. Meier Paul P. van der Werf Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis The Astrophysical Journal Star formation Giant molecular clouds Starburst galaxies Galactic center Interstellar medium |
| title | Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis |
| title_full | Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis |
| title_fullStr | Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis |
| title_full_unstemmed | Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis |
| title_short | Volume Density Structure of the Central Molecular Zone NGC 253 through ALCHEMI Excitation Analysis |
| title_sort | volume density structure of the central molecular zone ngc 253 through alchemi excitation analysis |
| topic | Star formation Giant molecular clouds Starburst galaxies Galactic center Interstellar medium |
| url | https://doi.org/10.3847/1538-4357/ad0e64 |
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