Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 493, Issue 2, Pages 2872-2909Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stz3525
Keywords
stars: formation; ISM: clouds; ISM: structure; galaxies: evolution; galaxies: ISM; galaxies: star formation
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group [KR4801/1-1]
- DFG Sachbeihilfe [KR4801/2-1]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme via the ERC Starting Grant MUSTANG [714907]
- Australia-Germany Joint Research Cooperation Scheme (UA-DAAD) [57387355]
- Australian Research Council [FT140101202]
- 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)
- Institut de Chimie/Institut de Physique (INC/INP)
- Commissariat a l'energie atomique et auxenergies alternatives (CEA)
- Centre national d'etudes spatiales (CNES)
- Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU
- INP
- Institut national de physique nucleaire et de physique des particules (IN2P3)
- CEA
- CNES
- ERC [694343, 726384]
- National Science Foundation (NSF) [1615105, 1615109, 1653300]
- National Aeronautics and Space Administration (NASA) Astrophysics Data Analysis Program (ADAP) [NNX16AF48G, NNX17AF39G]
- Natural Sciences and Engineering Research Council of Canada (NSERC) [RGPIN-2017-03987]
- Fondo de Fomento al Desarrollo Cientifico y Tecnologico of the Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT/FONDECYT), Programa de Iniciacion, Folio [11150220]
- DFG [SFB 881]
- Germany's Excellence Strategy (Heidelberg STRUCTURES Excellence Cluster) [EXC-2181/1-390900948]
- DFG in the form of an Emmy Noether Research Group [KR4598/2-1]
- MINECO/FEDER [AYA2016-79006-P]
- MCIU/AEI/FEDER [PGC2018-094671-B-I00]
- INSU/CNRS (France)
- MPG (Germany)
- IGN (Spain)
- European Research Council (ERC) [726384, 694343] Funding Source: European Research Council (ERC)
- STFC [ST/L00061X/1, ST/R000484/1] Funding Source: UKRI
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1615109] Funding Source: National Science Foundation
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It remains a major challenge to derive a theory of cloud-scale (less than or similar to 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-AINIA survey. We measure the spatially resolved (similar to 100 pc) CO-to-H alpha 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 Sigma(H2) >= 8 M-circle dot pc(-2), the GMC lifetime correlates with timescales for galactic dynamical processes, whereas at Sigma(H2) >= 8 M-circle dot 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 alpha (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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