New Constraints on the $^{12}$CO(2-1)/(1-0) Line Ratio Across Nearby Disc Galaxies
| Autor: | Christopher M Faesi, Sophia Stuber, M. J. Jimenez-Donaire, D. Chatzigiannakis, Erik Rosolowsky, Takashi Saito, Frank Bigiel, J. S. den Brok, Adam K. Leroy, L. Neumann, Daizhong Liu, Annie Hughes, Kathryn Grasha, Eva Schinnerer, J. Puschnig, Ashley T. Barnes, J. M. D. Kruijssen, A. Usero, M. Querejeta, Jérôme Pety, Andreas Schruba |
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| Přispěvatelé: | Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY) |
| Rok vydání: | 2021 |
| Předmět: |
Physics
radio lines: galaxies [PHYS]Physics [physics] Spiral galaxy 010308 nuclear & particles physics Star formation Order (ring theory) FOS: Physical sciences Astronomy and Astrophysics Astrophysics Radius Disc galaxy Astrophysics - Astrophysics of Galaxies 01 natural sciences Galaxy Space and Planetary Science Brightness temperature SM: molecules Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] 010303 astronomy & astrophysics Intensity (heat transfer) galaxies: ISM |
| Zdroj: | Monthly Notices of the Royal Astronomical Society Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P-Oxford Open Option A, 2021, 504 (3), pp.3221-3245. ⟨10.1093/mnras/stab859⟩ |
| ISSN: | 0035-8711 1365-2966 |
| DOI: | 10.48550/arxiv.2103.10442 |
| Popis: | Both the CO(2-1) and CO(1-0) lines are used to trace the mass of molecular gas in galaxies. Translating the molecular gas mass estimates between studies using different lines requires a good understanding of the behaviour of the CO(2-1)-to-CO(1-0) ratio, $R_{21}$. We compare new, high quality CO(1-0) data from the IRAM 30-m EMPIRE survey to the latest available CO(2-1) maps from HERACLES, PHANGS-ALMA, and a new IRAM 30-m M51 Large Program. This allows us to measure $R_{21}$ across the full star-forming disc of nine nearby, massive, star-forming spiral galaxies at 27" (${\sim} 1{-}2$ kpc) resolution. We find an average $R_{21} = 0.64\pm0.09$ when we take the luminosity-weighted mean of all individual galaxies. This result is consistent with the mean ratio for disc galaxies that we derive from single-pointing measurements in the literature, $R_{\rm 21, lit}~=~0.59^{+0.18}_{-0.09}$. The ratio shows weak radial variations compared to the point-to-point scatter in the data. In six out of nine targets the central enhancement in $R_{21}$ with respect to the galaxy-wide mean is of order $\sim 10{-}20\%$. We estimate an azimuthal scatter of $\sim$20% in $R_{21}$ at fixed galactocentric radius but this measurement is limited by our comparatively coarse resolution of 1.5 kpc. We find mild correlations between $R_{21}$ and CO brightness temperature, IR intensity, 70-to-160$ \mu$m ratio, and IR-to-CO ratio. All correlations indicate that $R_{21}$ increases with gas surface density, star formation rate surface density, and the interstellar radiation field. Comment: 27 pages, 18 figures, 5 tables; accepted for publication in MNRAS |
| Databáze: | OpenAIRE |
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