The lifecycle of molecular clouds in nearby star-forming disc galaxies
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) life...
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
2020
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2020, Volume: 493, Issue: 2, Pages: 2872-2909 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stz3525 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stz3525
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| Author Notes: | Mélanie Chevance, JM Diederik Kruijssen, Alexander PS Hygate, Andreas Schruba, Steven N Longmore, Brent Groves, Jonathan D Henshaw, Cinthya N Herrera, Annie Hughes, Sarah MR 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 CO Glover, Daniel T Haydon, I-Ting Ho, Kathryn Kreckel, Janice C Lee, Daizhong Liu, Miguel Querejeta, Toshiki Saito, Jiayi Sun, Antonio Usero and Dyas Utomo |
| Summary: | 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 $10\!-\!30\,{\rm Myr}$, and exhibit environmental variation, between and within galaxies. At kpc-scale molecular gas surface densities ΣH2≥8M⊙pc−2, the GMC lifetime correlates with time-scales for galactic dynamical processes, whereas at ΣH2≤8M⊙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. |
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| Item Description: | Advance access publication 2019 December 19 Gesehen am 15.04.2021 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/stz3525 |