Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA

Adam K. Leroy; Erik Rosolowsky; Antonio Usero; Karin Sandstrom; Eva Schinnerer; Andreas Schruba; Alberto D. Bolatto; Jiayi Sun; Ashley T. Barnes; Francesco Belfiore; Frank Bigiel; Jakob S. Den Brok; Yixian Cao; I. Da Chiang; Mélanie Chevance; Daniel A. Dale; Cosima Eibensteiner; Christopher M. Faesi; Simon C.O. Glover; Annie Hughes; María J. Jiménez Donaire; Ralf S. Klessen; Eric W. Koch; J. M.Diederik Kruijssen; Daizhong Liu; Sharon E. Meidt; Hsi An Pan; Jérôme Pety; Johannes Puschnig; Miguel Querejeta; Toshiki Saito; Amy Sardone; Elizabeth J. Watkins; Axel Weiss; Thomas G. Williams

doi:10.3847/1538-4357/ac3490

Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA

Adam K. Leroy
, Erik Rosolowsky
, Antonio Usero
, Karin Sandstrom
, Eva Schinnerer
, Andreas Schruba
, Alberto D. Bolatto
, Jiayi Sun
, Ashley T. Barnes
, Francesco Belfiore
, Frank Bigiel
, Jakob S. Den Brok
, Yixian Cao
, I. Da Chiang
, Mélanie Chevance
, Daniel A. Dale
, Cosima Eibensteiner
, Christopher M. Faesi
, Simon C.O. Glover
, Annie Hughes

María J. Jiménez Donaire, Ralf S. Klessen, Eric W. Koch, J. M.Diederik Kruijssen, Daizhong Liu, Sharon E. Meidt, Hsi An Pan, Jérôme Pety, Johannes Puschnig, Miguel Querejeta, Toshiki Saito, Amy Sardone, Elizabeth J. Watkins, Axel Weiss, Thomas G. Williams

Physics And Astronomy

Research output: Contribution to journal › Article › peer-review

102 Scopus citations

Abstract

We measure the low-J CO line ratios R 21 CO (2-1)/CO (1-0), R 32 CO (3-2)/CO (2-1), and R 31 CO (3-2)/CO (1-0) using whole-disk CO maps of nearby galaxies. We draw CO (2-1) from PHANGS-ALMA, HERACLES, and follow-up IRAM surveys; CO (1-0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO (3-2) from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey and Atacama Pathfinder Experiment Large APEX Sub-Millimetre Array mapping. All together, this yields 76, 47, and 29 maps of R 21, R 32, and R 31 at 20″ ∼1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log(M∗/Mo˙)=10.25-11, and star formation rate (SFR) = 1-5 M o˙ yr-1, dominate the sample. We find galaxy-integrated mean values and a 16%-84% range of R 21 = 0.65 (0.50-0.83), R 32 = 0.50 (0.23-0.59), and R 31 = 0.31 (0.20-0.42). We identify weak trends relating galaxy-integrated line ratios to properties expected to correlate with excitation, including SFR/M ∗ and SFR/L CO. Within galaxies, we measure central enhancements with respect to the galaxy-averaged value of ∼ 0.18-0.14+0.09 dex for R 21, 0.27-0.15+0.13 dex for R 31, and 0.08-0.09+0.11 dex for R 32. All three line ratios anticorrelate with galactocentric radius and positively correlate with the local SFR surface density and specific SFR, and we provide approximate fits to these relations. The observed ratios can be reasonably reproduced by models with low temperature, moderate opacity, and moderate densities, in good agreement with expectations for the cold interstellar medium. Because the line ratios are expected to anticorrelate with the CO (1-0)-to-H2 conversion factor, αCO1-0, these results have general implications for the interpretation of CO emission from galaxies.

Original language	English
Article number	149
Journal	Astrophysical Journal
Volume	927
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ac3490
State	Published - Mar 1 2022

Bibliographical note

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.

Funding

A.U. acknowledges support from Spanish funding grants PGC2018-094671-B-I00 (MCIU/AEI/FEDER) and PID2019-108765GB-I00 (MICINN). A.S. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903834. J.Pe. acknowledges support by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP, cofunded by CEA and CNES. This work is based on observations carried out under project Nos. 169-06, 053-07, 122-07, 160-06, 218-05, 058-08, 212-08, 196-13, 078-14, and 190-14 with the IRAM 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). We also thank the JCMT NGLS team and the JCMT staff for their hard work and making their data public, and we acknowledge helpful correspondence with the JCMT staff regarding calibration uncertainties. The James Clerk Maxwell Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada. R.S.K. and S.C.O.G. acknowledge funding from the European Research Council via the ERC Synergy Grant “ECOGAL—Understanding our Galactic ecosystem: From the disk of the Milky Way to the formation sites of stars and planets” (project ID 855130). They also acknowledge support from the DFG via the Collaborative Research Center (SFB 881, Project ID 138713538) “The Milky Way System” (subprojects A1, B1, B2, and B8) and the Heidelberg cluster of excellence (EXC 2181-390900948) “STRUCTURES: A unifying approach to emergent phenomena in the physical world, mathematics, and complex data,” funded by the German Excellence Strategy. M.Q. acknowledges support from the research project PID2019-106027GA-C44 from the Spanish Ministerio de Ciencia e Innovación. A.T.B., F.B., and J.d.B. would like to acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No.726384/Empire). E.S., H.A.P., T.S., and T.G.W. acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 694343). K.S. and I.D.C. acknowledge funding support from National Science Foundation grant No. 1615728 and NASA ADAP grants NNX16AF48G and NNX17AF39G. The work of A.K.L. and J.S. was partially supported by the National Science Foundation (NSF) under grant Nos. 1615105 and 1653300, as well as the National Aeronautics and Space Administration (NASA) under ADAP grants NNX16AF48G and NNX17AF39G. M.C. and J.M.D.K. gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) in the form of the Emmy Noether Research Group (grant No. KR4801/1-1) and the DFG Sachbeihilfe (grant No. LR4801/2-1), as well as the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG (grant agreement No. 714907). E.R. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference No. RGPIN-2017-03987, and computational support from Compute Canada. C.E. acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG) Sachbeihilfe, grant No. BI1546/3-1.

Funders	Funder number
Ministerio de Ciencia, Innovación y Universidades
Albert Ellis Institute
Astronomy and Astrophysics Postdoctoral Fellowship
Centre National d’Etudes Spatiales
INSU
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Instituto Nacional del Cáncer
Engineering Research Centers
CNRS Programme National Physique Chimie du Milieu Interstellaire
CNRS Centre National de la Recherche Scientifique
California Earthquake Authority
Instituto Nacional de Pediatria
Science and Technology Facilities Council of the United Kingdom
Spanish Ministerio de Ciencia e innovación
H2020 European Research Council
National Research Council Canada (NRCC)
Horizon 2020
National Science Foundation Arctic Social Science Program	1615728, 1653300, AST-1903834, 1615105
National Aeronautics and Space Administration	NNX17AF39G, NNX16AF48G
Horizon 2020 Framework Programme	694343, 726384, 714907, 855130
DFG Sachbeihilfe	LR4801/2-1
Deutsche Forschungsgemeinschaft	138713538, BI1546/3-1, KR4801/1-1
German Excellence Strategy in the Heidelberg Cluster of Excellence STRUCTURES	EXC 2181-390900948
Natural Sciences and Engineering Research Council of Canada	RGPIN-2017-03987
European Regional Development Fund	PID2019-108765GB-I00

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.3847/1538-4357/ac3490

Cite this

Leroy, A. K., Rosolowsky, E., Usero, A., Sandstrom, K., Schinnerer, E., Schruba, A., Bolatto, A. D., Sun, J., Barnes, A. T., Belfiore, F., Bigiel, F., Den Brok, J. S., Cao, Y., Chiang, I. D., Chevance, M., Dale, D. A., Eibensteiner, C., Faesi, C. M., Glover, S. C. O., ... Williams, T. G. (2022). Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA. Astrophysical Journal, 927(2), Article 149. https://doi.org/10.3847/1538-4357/ac3490

@article{bc03393df2ba447d8d860410c0025f0e,

title = "Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA",

abstract = "We measure the low-J CO line ratios R 21 CO (2-1)/CO (1-0), R 32 CO (3-2)/CO (2-1), and R 31 CO (3-2)/CO (1-0) using whole-disk CO maps of nearby galaxies. We draw CO (2-1) from PHANGS-ALMA, HERACLES, and follow-up IRAM surveys; CO (1-0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO (3-2) from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey and Atacama Pathfinder Experiment Large APEX Sub-Millimetre Array mapping. All together, this yields 76, 47, and 29 maps of R 21, R 32, and R 31 at 20″ ∼1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log(M∗/Mo˙)=10.25-11, and star formation rate (SFR) = 1-5 M o˙ yr-1, dominate the sample. We find galaxy-integrated mean values and a 16\%-84\% range of R 21 = 0.65 (0.50-0.83), R 32 = 0.50 (0.23-0.59), and R 31 = 0.31 (0.20-0.42). We identify weak trends relating galaxy-integrated line ratios to properties expected to correlate with excitation, including SFR/M ∗ and SFR/L CO. Within galaxies, we measure central enhancements with respect to the galaxy-averaged value of ∼ 0.18-0.14+0.09 dex for R 21, 0.27-0.15+0.13 dex for R 31, and 0.08-0.09+0.11 dex for R 32. All three line ratios anticorrelate with galactocentric radius and positively correlate with the local SFR surface density and specific SFR, and we provide approximate fits to these relations. The observed ratios can be reasonably reproduced by models with low temperature, moderate opacity, and moderate densities, in good agreement with expectations for the cold interstellar medium. Because the line ratios are expected to anticorrelate with the CO (1-0)-to-H2 conversion factor, αCO1-0, these results have general implications for the interpretation of CO emission from galaxies.",

author = "Leroy, \{Adam K.\} and Erik Rosolowsky and Antonio Usero and Karin Sandstrom and Eva Schinnerer and Andreas Schruba and Bolatto, \{Alberto D.\} and Jiayi Sun and Barnes, \{Ashley T.\} and Francesco Belfiore and Frank Bigiel and \{Den Brok\}, \{Jakob S.\} and Yixian Cao and Chiang, \{I. Da\} and M{\'e}lanie Chevance and Dale, \{Daniel A.\} and Cosima Eibensteiner and Faesi, \{Christopher M.\} and Glover, \{Simon C.O.\} and Annie Hughes and \{Jim{\'e}nez Donaire\}, \{Mar{\'i}a J.\} and Klessen, \{Ralf S.\} and Koch, \{Eric W.\} and Kruijssen, \{J. M.Diederik\} and Daizhong Liu and Meidt, \{Sharon E.\} and Pan, \{Hsi An\} and J{\'e}r{\^o}me Pety and Johannes Puschnig and Miguel Querejeta and Toshiki Saito and Amy Sardone and Watkins, \{Elizabeth J.\} and Axel Weiss and Williams, \{Thomas G.\}",

note = "Publisher Copyright: {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society.",

year = "2022",

month = mar,

day = "1",

doi = "10.3847/1538-4357/ac3490",

language = "English",

volume = "927",

number = "2",

}

Leroy, AK, Rosolowsky, E, Usero, A, Sandstrom, K, Schinnerer, E, Schruba, A, Bolatto, AD, Sun, J, Barnes, AT, Belfiore, F, Bigiel, F, Den Brok, JS, Cao, Y, Chiang, ID, Chevance, M, Dale, DA, Eibensteiner, C, Faesi, CM, Glover, SCO, Hughes, A, Jiménez Donaire, MJ, Klessen, RS, Koch, EW, Kruijssen, JMD, Liu, D, Meidt, SE, Pan, HA, Pety, J, Puschnig, J, Querejeta, M, Saito, T, Sardone, A, Watkins, EJ, Weiss, A & Williams, TG 2022, 'Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA', Astrophysical Journal, vol. 927, no. 2, 149. https://doi.org/10.3847/1538-4357/ac3490

TY - JOUR

T1 - Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA

AU - Leroy, Adam K.

AU - Rosolowsky, Erik

AU - Usero, Antonio

AU - Sandstrom, Karin

AU - Schinnerer, Eva

AU - Schruba, Andreas

AU - Bolatto, Alberto D.

AU - Sun, Jiayi

AU - Barnes, Ashley T.

AU - Belfiore, Francesco

AU - Bigiel, Frank

AU - Den Brok, Jakob S.

AU - Cao, Yixian

AU - Chiang, I. Da

AU - Chevance, Mélanie

AU - Dale, Daniel A.

AU - Eibensteiner, Cosima

AU - Faesi, Christopher M.

AU - Glover, Simon C.O.

AU - Hughes, Annie

AU - Jiménez Donaire, María J.

AU - Klessen, Ralf S.

AU - Koch, Eric W.

AU - Kruijssen, J. M.Diederik

AU - Liu, Daizhong

AU - Meidt, Sharon E.

AU - Pan, Hsi An

AU - Pety, Jérôme

AU - Puschnig, Johannes

AU - Querejeta, Miguel

AU - Saito, Toshiki

AU - Sardone, Amy

AU - Watkins, Elizabeth J.

AU - Weiss, Axel

AU - Williams, Thomas G.

PY - 2022/3/1

Y1 - 2022/3/1

N2 - We measure the low-J CO line ratios R 21 CO (2-1)/CO (1-0), R 32 CO (3-2)/CO (2-1), and R 31 CO (3-2)/CO (1-0) using whole-disk CO maps of nearby galaxies. We draw CO (2-1) from PHANGS-ALMA, HERACLES, and follow-up IRAM surveys; CO (1-0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO (3-2) from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey and Atacama Pathfinder Experiment Large APEX Sub-Millimetre Array mapping. All together, this yields 76, 47, and 29 maps of R 21, R 32, and R 31 at 20″ ∼1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log(M∗/Mo˙)=10.25-11, and star formation rate (SFR) = 1-5 M o˙ yr-1, dominate the sample. We find galaxy-integrated mean values and a 16%-84% range of R 21 = 0.65 (0.50-0.83), R 32 = 0.50 (0.23-0.59), and R 31 = 0.31 (0.20-0.42). We identify weak trends relating galaxy-integrated line ratios to properties expected to correlate with excitation, including SFR/M ∗ and SFR/L CO. Within galaxies, we measure central enhancements with respect to the galaxy-averaged value of ∼ 0.18-0.14+0.09 dex for R 21, 0.27-0.15+0.13 dex for R 31, and 0.08-0.09+0.11 dex for R 32. All three line ratios anticorrelate with galactocentric radius and positively correlate with the local SFR surface density and specific SFR, and we provide approximate fits to these relations. The observed ratios can be reasonably reproduced by models with low temperature, moderate opacity, and moderate densities, in good agreement with expectations for the cold interstellar medium. Because the line ratios are expected to anticorrelate with the CO (1-0)-to-H2 conversion factor, αCO1-0, these results have general implications for the interpretation of CO emission from galaxies.

AB - We measure the low-J CO line ratios R 21 CO (2-1)/CO (1-0), R 32 CO (3-2)/CO (2-1), and R 31 CO (3-2)/CO (1-0) using whole-disk CO maps of nearby galaxies. We draw CO (2-1) from PHANGS-ALMA, HERACLES, and follow-up IRAM surveys; CO (1-0) from COMING and the Nobeyama CO Atlas of Nearby Spiral Galaxies; and CO (3-2) from the James Clerk Maxwell Telescope Nearby Galaxy Legacy Survey and Atacama Pathfinder Experiment Large APEX Sub-Millimetre Array mapping. All together, this yields 76, 47, and 29 maps of R 21, R 32, and R 31 at 20″ ∼1.3 kpc resolution, covering 43, 34, and 20 galaxies. Disk galaxies with high stellar mass, log(M∗/Mo˙)=10.25-11, and star formation rate (SFR) = 1-5 M o˙ yr-1, dominate the sample. We find galaxy-integrated mean values and a 16%-84% range of R 21 = 0.65 (0.50-0.83), R 32 = 0.50 (0.23-0.59), and R 31 = 0.31 (0.20-0.42). We identify weak trends relating galaxy-integrated line ratios to properties expected to correlate with excitation, including SFR/M ∗ and SFR/L CO. Within galaxies, we measure central enhancements with respect to the galaxy-averaged value of ∼ 0.18-0.14+0.09 dex for R 21, 0.27-0.15+0.13 dex for R 31, and 0.08-0.09+0.11 dex for R 32. All three line ratios anticorrelate with galactocentric radius and positively correlate with the local SFR surface density and specific SFR, and we provide approximate fits to these relations. The observed ratios can be reasonably reproduced by models with low temperature, moderate opacity, and moderate densities, in good agreement with expectations for the cold interstellar medium. Because the line ratios are expected to anticorrelate with the CO (1-0)-to-H2 conversion factor, αCO1-0, these results have general implications for the interpretation of CO emission from galaxies.

UR - https://www.scopus.com/pages/publications/85126603692

UR - https://www.scopus.com/pages/publications/85126603692#tab=citedBy

U2 - 10.3847/1538-4357/ac3490

DO - 10.3847/1538-4357/ac3490

M3 - Article

AN - SCOPUS:85126603692

SN - 0004-637X

VL - 927

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 149

ER -

Low- J CO Line Ratios from Single-dish CO Mapping Surveys and PHANGS-ALMA

Abstract

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