Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82
The distribution and physical conditions of molecular gas are closely linked to star formation and the subsequent evolution of galaxies. Emission from carbon monoxide (CO) and its isotopologues traces the bulk of molecular gas and provides constraints on the physical conditions through their line ra...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adb579 |
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| author | Valencia Zhang Jakob den Brok Qizhou Zhang Yu-Hsuan Teng María J. Jiménez-Donaire Eric W. Koch Antonio Usero Fabian Walter Leindert Boogaard Craig Yanitski Cosima Eibensteiner Ivana Bešlic Juan Luis Verbena |
| author_facet | Valencia Zhang Jakob den Brok Qizhou Zhang Yu-Hsuan Teng María J. Jiménez-Donaire Eric W. Koch Antonio Usero Fabian Walter Leindert Boogaard Craig Yanitski Cosima Eibensteiner Ivana Bešlic Juan Luis Verbena |
| author_sort | Valencia Zhang |
| collection | DOAJ |
| description | The distribution and physical conditions of molecular gas are closely linked to star formation and the subsequent evolution of galaxies. Emission from carbon monoxide (CO) and its isotopologues traces the bulk of molecular gas and provides constraints on the physical conditions through their line ratios. However, a comprehensive understanding of how the particular choice of line modeling approach impacts derived molecular properties remains incomplete. Here, we study the nearby starburst galaxy M82, known for its intense star formation and molecular emission, using the large set of available multi-CO line observations. We present high-resolution (∼85 pc) emission of seven CO isotopologue lines, including ^12 CO, ^13 CO, and C ^18 O from the J = 1–0, 2–1, and 3–2 transitions. Using RADEX for radiative transfer modeling, we analyze M82’s molecular properties with (i) a one-zone model and (ii) a variable density model, comparing observed and simulated emissions via a minimum χ ^2 analysis. We find that inferred gas conditions—kinetic temperature and density—are consistent across models, with minimal statistical differences. However, due to their low critical densities (<10 ^4 cm ^−3 ), low- J CO isotopologue lines do not effectively probe higher-density gas prevalent in starburst environments like that of M82. Our results further imply that this limitation extends to high-redshift ( z ⪆ 1) galaxies with similar conditions, where low- J CO lines are inadequate for density constraints. Future studies of extreme star-forming regions like M82 will require higher- J CO lines or alternative molecular tracers with higher critical densities. |
| format | Article |
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| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-4dc7ee4fd4e345c1935426445c45bf622025-08-20T02:56:44ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198212110.3847/1538-4357/adb579Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82Valencia Zhang0https://orcid.org/0009-0007-2660-7635Jakob den Brok1https://orcid.org/0000-0002-8760-6157Qizhou Zhang2https://orcid.org/0000-0003-2384-6589Yu-Hsuan Teng3https://orcid.org/0000-0003-4209-1599María J. Jiménez-Donaire4https://orcid.org/0000-0002-9165-8080Eric W. Koch5https://orcid.org/0000-0001-9605-780XAntonio Usero6https://orcid.org/0000-0003-1242-505XFabian Walter7https://orcid.org/0000-0003-4793-7880Leindert Boogaard8https://orcid.org/0000-0002-3952-8588Craig Yanitski9https://orcid.org/0009-0009-3294-6320Cosima Eibensteiner10https://orcid.org/0000-0002-1185-2810Ivana Bešlic11https://orcid.org/0000-0003-0583-7363Juan Luis Verbena12https://orcid.org/0000-0001-8835-218XCenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; valenciaz2025@gmail.com, jakob.denbrok@gmail.com; Phillips Academy , Andover, MA 01810, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; valenciaz2025@gmail.com, jakob.denbrok@gmail.comCenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; valenciaz2025@gmail.com, jakob.denbrok@gmail.comDepartment of Astronomy, University of Maryland , 4296 Stadium Drive, College Park, MD 20742, USAObservatorio Astronómico Nacional (IGN) , C/Alfonso XII, 3, E-28014 Madrid, Spain; Centro de Desarrollos Tecnológicos , Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, SpainCenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138, USA ; valenciaz2025@gmail.com, jakob.denbrok@gmail.comObservatorio Astronómico Nacional (IGN) , C/Alfonso XII, 3, E-28014 Madrid, SpainMax-Planck-Institut für Astronomie , Königstuhl 17, D-69117, Heidelberg, GermanyLeiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, The NetherlandsI. Physikalisches Institut der Universität zu Köln , Zülpicher Straße 77, 50937, Köln, GermanyNational Radio Astronomy Observatory , 520 Edgemont Road, Charlottesville, VA 22903, USASorbonne Université , Observatoire de Paris, Université PSL, CNRS, LERMA, F-75014, Paris, FranceI. Physikalisches Institut der Universität zu Köln , Zülpicher Straße 77, 50937, Köln, GermanyThe distribution and physical conditions of molecular gas are closely linked to star formation and the subsequent evolution of galaxies. Emission from carbon monoxide (CO) and its isotopologues traces the bulk of molecular gas and provides constraints on the physical conditions through their line ratios. However, a comprehensive understanding of how the particular choice of line modeling approach impacts derived molecular properties remains incomplete. Here, we study the nearby starburst galaxy M82, known for its intense star formation and molecular emission, using the large set of available multi-CO line observations. We present high-resolution (∼85 pc) emission of seven CO isotopologue lines, including ^12 CO, ^13 CO, and C ^18 O from the J = 1–0, 2–1, and 3–2 transitions. Using RADEX for radiative transfer modeling, we analyze M82’s molecular properties with (i) a one-zone model and (ii) a variable density model, comparing observed and simulated emissions via a minimum χ ^2 analysis. We find that inferred gas conditions—kinetic temperature and density—are consistent across models, with minimal statistical differences. However, due to their low critical densities (<10 ^4 cm ^−3 ), low- J CO isotopologue lines do not effectively probe higher-density gas prevalent in starburst environments like that of M82. Our results further imply that this limitation extends to high-redshift ( z ⪆ 1) galaxies with similar conditions, where low- J CO lines are inadequate for density constraints. Future studies of extreme star-forming regions like M82 will require higher- J CO lines or alternative molecular tracers with higher critical densities.https://doi.org/10.3847/1538-4357/adb579Starburst galaxiesInterstellar mediumMolecular gasMolecular spectroscopyMillimeter-wave spectroscopyStar formation |
| spellingShingle | Valencia Zhang Jakob den Brok Qizhou Zhang Yu-Hsuan Teng María J. Jiménez-Donaire Eric W. Koch Antonio Usero Fabian Walter Leindert Boogaard Craig Yanitski Cosima Eibensteiner Ivana Bešlic Juan Luis Verbena Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 The Astrophysical Journal Starburst galaxies Interstellar medium Molecular gas Molecular spectroscopy Millimeter-wave spectroscopy Star formation |
| title | Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 |
| title_full | Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 |
| title_fullStr | Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 |
| title_full_unstemmed | Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 |
| title_short | Application of Resolved Low-J Multi-CO Line Modeling with RADEX to Constrain the Molecular Gas Properties in the Starburst M82 |
| title_sort | application of resolved low j multi co line modeling with radex to constrain the molecular gas properties in the starburst m82 |
| topic | Starburst galaxies Interstellar medium Molecular gas Molecular spectroscopy Millimeter-wave spectroscopy Star formation |
| url | https://doi.org/10.3847/1538-4357/adb579 |
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