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The lifecycle of molecular clouds in nearby star-forming disc galaxies

Chevance, Mélanie and Kruijssen, J M Diederik and Hygate, Alexander P. S. and Schruba, Andreas and Longmore, Steven N. and Groves, Brent and Henshaw, Jonathan D. and Herrera, Cinthya N. and Hughes, Annie and Jeffreson, Sarah M. R, and Lang, Philipp and Leroy, Adam K. and Meidt, Sharon E. and Pety, Jérôme and Razza, Alessandro and Rosolowsky, Erik and Schinnerer, Eva and Bigiel, Frank and Blanc, Guillermo A. and Emsellem, Eric and Faesi, Christopher M. and Glover, Simon C. O. and Haydon, Daniel T. and Ho, I-Ting and Kreckel, Kathryn and Lee, Janice C. and Liu, Daizhong and Querejeta, Miguel and Saito, Toshiki and Sun, Jiayi and Usero, Antonio and Utomo, Dyas (2020) The lifecycle of molecular clouds in nearby star-forming disc galaxies. Monthly Notices of the Royal Astronomical Society, 493 (2). pp. 2872-2909. ISSN 0035-8711.

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It remains a major challenge to derive a theory of cloud-scale (⁠≲100 pc) star formation and feedback, describing how galaxies convert gas into stars as a function of the galactic environment. Progress has been hampered by a lack of robust empirical constraints on the giant molecular cloud (GMC) lifecycle. We address this problem by systematically applying a new statistical method for measuring the evolutionary timeline of the GMC lifecycle, star formation, and feedback to a sample of nine nearby disc galaxies, observed as part of the PHANGS-ALMA survey. We measure the spatially resolved (∼100 pc) CO-to-H α flux ratio and find a universal de-correlation between molecular gas and young stars on GMC scales, allowing us to quantify the underlying evolutionary timeline. GMC lifetimes are short, typically 10−30 Myr⁠, and exhibit environmental variation, between and within galaxies. At kpc-scale molecular gas surface densities Σ_(H₂) ≥ 8 M_⊙ pc⁻²⁠, the GMC lifetime correlates with time-scales for galactic dynamical processes, whereas at Σ_(H₂) ≤ 8 M_⊙ pc⁻² GMCs decouple from galactic dynamics and live for an internal dynamical time-scale. After a long inert phase without massive star formation traced by H α (75–90 per cent of the cloud lifetime), GMCs disperse within just 1−5 Myr once massive stars emerge. The dispersal is most likely due to early stellar feedback, causing GMCs to achieve integrated star formation efficiencies of 4–10 per cent. These results show that galactic star formation is governed by cloud-scale, environmentally dependent, dynamical processes driving rapid evolutionary cycling. GMCs and H II regions are the fundamental units undergoing these lifecycles, with mean separations of 100−300 pc in star-forming discs. Future work should characterize the multiscale physics and mass flows driving these lifecycles.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Chevance, Mélanie0000-0002-5635-5180
Kruijssen, J M Diederik0000-0002-8804-0212
Hygate, Alexander P. S.0000-0002-6488-471X
Groves, Brent0000-0002-9768-0246
Henshaw, Jonathan D.0000-0001-9656-7682
Hughes, Annie0000-0002-9181-1161
Leroy, Adam K.0000-0002-2545-1700
Meidt, Sharon E.0000-0002-6118-4048
Pety, Jérôme0000-0003-3061-6546
Razza, Alessandro0000-0001-7876-1713
Rosolowsky, Erik0000-0002-5204-2259
Schinnerer, Eva0000-0002-3933-7677
Bigiel, Frank0000-0003-0166-9745
Blanc, Guillermo A.0000-0003-4218-3944
Emsellem, Eric0000-0002-6155-7166
Glover, Simon C. O.0000-0001-6708-1317
Haydon, Daniel T.0000-0002-3805-7913
Ho, I-Ting0000-0002-0757-9559
Kreckel, Kathryn0000-0001-6551-3091
Lee, Janice C.0000-0002-2278-9407
Liu, Daizhong0000-0001-9773-7479
Querejeta, Miguel0000-0002-0472-1011
Saito, Toshiki0000-0002-2501-9328
Sun, Jiayi0000-0003-0378-4667
Usero, Antonio0000-0003-1242-505X
Utomo, Dyas0000-0003-4161-2639
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 December 9. Received 2019 November 6; in original form 2019 August 31. We thank an anonymous referee for a helpful report, as well as Bruce Elmegreen, Mark Heyer, Benjamin Keller, Jenny (Jaeyeon) Kim, Jeong-Gyu Kim, Eve Ostriker, Mark Krumholz, Jacob Ward, and Brad Whitmore for helpful discussions and/or comments. MC and JMDK gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1) and the DFG Sachbeihilfe (grant number KR4801/2-1). JMDK, APSH, SMRJ, and DTH gratefully acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG (grant agreement number 714907). MC, JMDK, SMRJ, and DTH acknowledge support from the Australia-Germany Joint Research Cooperation Scheme (UA-DAAD, grant number 57387355). APSH, SMRJ, and DTH are fellows of the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD). BG gratefully acknowledges the support of the Australian Research Council as the recipient of a Future Fellowship (FT140101202). CNC, AH, and JP acknowledge funding from the Programme National ‘Physique et Chimie du Milieu Interstellaire’ (PCMI) of the Centre national de la recherche scientifique/Institut national des sciences de l’Univers (CNRS/INSU) with the Institut de Chimie/Institut de Physique (INC/INP), co-funded by the Commissariat à l'énergie atomique et aux énergies alternatives (CEA) and the Centre national d'études spatiales (CNES). AH acknowledges support by the Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU with the INP and the Institut national de physique nucléaire et de physique des particules (IN2P3), co-funded by CEA and CNES. PL, ES, CF, DL, and TS acknowledge funding from the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 694343). The work of AKL, JS, and DU is partially supported by the National Science Foundation (NSF) under Grants No. 1615105, 1615109, and 1653300. AKL also acknowledges partial support from the National Aeronautics and Space Administration (NASA) Astrophysics Data Analysis Program (ADAP) grants NNX16AF48G and NNX17AF39G. ER acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number RGPIN-2017-03987. FB acknowledges funding from the ERC under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 726384). GB is supported by the Fondo de Fomento al Desarrollo Científico y Tecnológico of theComisión Nacional de Investigación Científica y Tecnológica (CONICYT/FONDECYT), Programa de Iniciación, Folio 11150220. SCOG acknowledges support from the DFG via SFB 881 ‘The Milky Way System’ (subprojects B1, B2, and B8) and also via Germany’s Excellence Strategy EXC-2181/1–390900948 (the Heidelberg STRUCTURES Excellence Cluster). KK gratefully acknowledges funding from the DFG in the form of an Emmy Noether Research Group (grant number KR4598/2-1, PI Kreckel). AU acknowledges support from the Spanish funding grants AYA2016-79006-P (MINECO/FEDER) and PGC2018-094671-B-I00 (MCIU/AEI/FEDER). This work was carried out as part of the PHANGS collaboration. This paper makes use of the following ALMA data: ADS/JAO.ALMA #2012.1.00650.S, ADS/JAO.ALMA #2015.1.00925.S, ADS/JAO.ALMA #2015.1.00956.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This paper makes use of the PdBI Arcsecond Whirlpool Survey (Pety et al. 2013; Schinnerer et al. 2013). The IRAM 30-m telescope and PdBI are run by IRAM, which is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). The results presented in this paper made use of THINGS, ‘The HI Nearby Galaxy Survey’ (Walter et al. 2008). This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)KR4801/1-1
Deutsche Forschungsgemeinschaft (DFG)KR4801/2-1
European Research Council (ERC)714907
Australia-Germany Joint Research Cooperation Scheme57387355
International Max Planck Research School for Astronomy and Cosmic PhysicsUNSPECIFIED
Australian Research CouncilFT140101202
Programme National Physique et Chimie du Milieu Interstellaire (PCMI)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Institut de Chimie/Institut de Physique (INC/INP)UNSPECIFIED
Commissariat a l'Energie Atomique (CEA)UNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Programme National Galaxies et Cosmologie (PNCG)UNSPECIFIED
Institut National de Physique Nucléaire et de Physique des Particules (IN2P3)UNSPECIFIED
European Research Council (ERC)694343
Natural Sciences and Engineering Research Council of Canada (NSERC)RGPIN-2017-03987
European Research Council (ERC)726384
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)11150220
Deutsche Forschungsgemeinschaft (DFG)SFB 881
Heidelberg STRUCTURES Excellence ClusterEXC-2181/1-390900948
Deutsche Forschungsgemeinschaft (DFG)KR4598/2-1
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2016-79006-P
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Ministerio de Ciencia, Innovación y Universidades (MICIU)PGC2018-094671-B-I00
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:stars: formation, ISM: clouds, ISM: structure, galaxies: evolution, galaxies: ISM, galaxies: star formation
Issue or Number:2
Record Number:CaltechAUTHORS:20200430-151241108
Persistent URL:
Official Citation:Mélanie Chevance, J M Diederik Kruijssen, Alexander P S Hygate, Andreas Schruba, Steven N Longmore, Brent Groves, Jonathan D Henshaw, Cinthya N Herrera, Annie Hughes, Sarah M R Jeffreson, Philipp Lang, Adam K Leroy, Sharon E Meidt, Jérôme Pety, Alessandro Razza, Erik Rosolowsky, Eva Schinnerer, Frank Bigiel, Guillermo A Blanc, Eric Emsellem, Christopher M Faesi, Simon C O Glover, Daniel T Haydon, I-Ting Ho, Kathryn Kreckel, Janice C Lee, Daizhong Liu, Miguel Querejeta, Toshiki Saito, Jiayi Sun, Antonio Usero, Dyas Utomo, The lifecycle of molecular clouds in nearby star-forming disc galaxies, Monthly Notices of the Royal Astronomical Society, Volume 493, Issue 2, April 2020, Pages 2872–2909,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102949
Deposited By: George Porter
Deposited On:01 May 2020 14:20
Last Modified:01 May 2020 14:20

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