Suchergebnisse

Aims. The complexity of star formation at the physical scale of molecular clouds is not yet fully understood. We investigate the mechanisms regulating the formation of stars in di erent environments within nearby star-forming galaxies from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) sample. Methods. Integral field spectroscopic data and radio-interferometric observations of 18 galaxies were combined to explore the existence of the resolved star formation main sequence ( stellar versus SFR), resolved Kennicutt–Schmidt relation ( mol: gas versus SFR), and resolved molecular gas main sequence ( stellar versus mol: gas), and we derived their slope and scatter at spatial resolutions from 100 pc to 1 kpc (under various assumptions). Results. All three relations were recovered at the highest spatial resolution (100 pc). Furthermore, significant variations in these scaling relations were observed across di erent galactic environments. The exclusion of non-detections has a systematic impact on the inferred slope as a function of the spatial scale. Finally, the scatter of the mol: gas+stellar versus SFR correlation is smaller than that of the resolved star formation main sequence, but higher than that found for the resolved Kennicutt–Schmidt relation. Conclusions. The resolved molecular gas main sequence has the tightest relation at a spatial scale of 100 pc (scatter of 0:34 dex), followed by the resolved Kennicutt–Schmidt relation (0:41 dex) and then the resolved star formation main sequence (0:51 dex). This is consistent with expectations from the timescales involved in the evolutionary cycle of molecular clouds. Surprisingly, the resolved Kennicutt–Schmidt relation shows the least variation across galaxies and environments, suggesting a tight link between molecular gas and subsequent star formation. The scatter of the three relations decreases at lower spatial resolutions, with the resolved Kennicutt–Schmidt relation being the tightest (0:27 dex) at a spatial scale of 1 kpc. Variation in the slope of the resolved star formation main sequence among galaxies is partially due to di erent detection fractions of SFR with respect to stellar. ; European Research Council (ERC) 694343 726384/Empire National Science Foundation (NSF) 1615105 1615109 1653300 ANID project Basal AFB-170002 German Research Foundation (DFG) KR4801/1-1 German Research Foundation (DFG) European Commission KR4801/2-1 SFB 881 138713538 European Research Council (ERC) 714907 German Research Foundation (DFG) KR4598/2-1 Instituto de Salud Carlos III Spanish Government PID2019-106027GA-C44 Spanish funding grant (MINECO/FEDER) AYA2016-79006-P Spanish funding grant (MCIU/AEI/FEDER) PGC2018-094671-B-I00 Spanish funding grant (MICINN) PID2019-108765GB-I00 European Research Council (ERC) European Commission 855130 Heidelberg cluster of excellence - German Excellence Strategy EXC 2181 - 390900948 European Organisation for Astronomical Research in the Southern Hemisphere under ESO 094.C-0623 098.C-0484 1100.B-0651 ; Versión publicada - versión final del editor

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 mu m images. At the simplest level, we distinguish five environments: centres, bars, spiral arms, interarm regions, and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, which are publicly released but not explicitly used in this paper. We examine trends with environment in the molecular gas content, star formation rate, and depletion time using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals clearly dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties and without significant slope differences among environments. In contrast to what has been suggested by early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle. ; Instituto de Salud Carlos III Spanish Government PID2019-106027GA-C44 European Research Council (ERC) 694343 National Science Foundation (NSF) National Research Foundation of Korea 1615105 1615109 1653300 National Aeronautics and Space Administration (NASA) under ADAP grants NNX16AF48G NNX17AF39G German Research Foundation (DFG) SFB 881 138713538 Heidelberg Cluster of Excellence "STRUCTURES" in the framework of Germany's Excellence Strategy EXC-2181/1 390900948 European Research Council via the ERC Synergy Grant "ECOGAL" 855130 SKA South Africa 694343 721463 726384/Empire Academy of Finland 297738 German Research Foundation (DFG) KR4801/1-1 KR4598/2-1 KR4801/2-1 BI1546/3-1 European Research Council (ERC) 714907 National Science Foundation (NSF) 1903946 Spanish Government AYA2016-79006-P Spanish Government European Commission PID2019-108765GB-I00 Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU INP IN2P3 French Atomic Energy Commission Centre National D'etudes Spatiales Programme National 'Physique et Chimie du Milieu Interstellaire' (PCMI) of CNRS/INSU INC/INP - CEA Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2017-03987 Spanish funding grant (MINECO/FEDER) AYA2016-79006-P Spanish funding grant (MCIU/AEI/FEDER) PGC2018-094671-B-I00 Spanish funding grant (MICINN) PID2019-108765GB-I00 German Research Foundation (DFG) 138713538 - SFB 881 ; Versión sometida a revisión - Preprint