Variations in the Σ_(SFR)−Σ_(mol)−Σ_(*) plane across galactic environments in PHANGS galaxies

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Aims. There exists some consensus that the stellar mass surface density (Σ_(*)) and molecular gas mass surface density (Σ_(mol)) are the main quantities responsible for locally setting the star formation rate. This regulation is inferred from locally resolved scaling relations between these two quantities and the star formation rate surface density (Σ_(SFR)), which have been extensively studied in a wide variety of works. However, the universality of these relations is debated. Here, we probe the interplay between these three quantities across different galactic environments at a spatial resolution of 150 pc. Methods. We performed a hierarchical Bayesian linear regression to find the best set of parameters C_(*), C_(mol), and C_(norm) that describe the starforming plane conformed by Σ_(*), Σ_(mol), and Σ_(SFR), such that log Σ_(SFR) = C_(*) log Σ(*) + C_(mol) log Σ_(mol) + C_(norm). We also explored variations in the determined parameters across galactic environments, focusing our analysis on the C_(*) and C_(mol) slopes. Results. We find signs of variations in the posterior distributions of C(*) and C_(mol) across different galactic environments. The dependence of Σ_(SFR) on Σ_(*) spans a wide range of slopes, with negative and positive values, while the dependence of Σ_(SFR) on Σ_(mol) is always positive. Bars show the most negative value of C_(*) (−0.41), which is a sign of longer depletion times, while spiral arms show the highest C_(*) among all environments (0.45). Variations in C_(mol) also exist, although they are more subtle than those found for C_(*). Conclusions. We conclude that systematic variations in the interplay of Σ_(*), Σ_(mol), and Σ_(SFR) across different galactic environments exist at a spatial resolution of 150 pc, and we interpret these variations to be produced by an additional mechanism regulating the formation of stars that is not captured by either Σ_(*) or Σ_(mol). Studying environmental variations in single galaxies, we find that these variations correlate with changes in the star formation efficiency across environments, which could be linked to the dynamical state of the gas that prevents it from collapsing and forming stars, or to changes in the molecular gas fraction.
© I. Pessa et al. 2022. Artículo firmado por 29 autores. This work was carried out as part of the PHANGS collaboration. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes IDs 094.C-0623, 098.C-0484 and 1100.B-0651. This paper also makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.01161.S, ADS/JAO.ALMA#2015.1.00925.S, ADS/JAO.ALMA#2015.1.00956.S and ADS/JAO.ALMA#2017.1.00886.L. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST 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. M.C. and J.M.D.K. gratefully acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through an Emmy Noether Research Group (grant number KR4801/1-1), as well as 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). J.G. gratefully acknowledges financial support from the Swiss National Science Foundation (grant no CRSII5_193826). K.K. gratefully acknowledges funding from the German Research Foundation (DFG) in the form of an Emmy Noether Research Group (grant number KR4598/2-1, P.I.: Kreckel). E.W.K. acknowledges support from the Smithsonian Institution as a Submillimeter Array (SMA) Fellow. E.R. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number RGPIN-2017-03987. M.Q. acknowledges support from the Spanish grant PID2019-106027GA-C44, funded by MCIN/AEI/10.13039/501100011033. G.A.B. gratefully acknowledges support by the ANID BASAL project FB210003. J.Pe. acknowledges support by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP, co-funded by CEA and CNES. J.Pe acknowledges support from the ANR grant ANR-21-CE31-0010. R.S.K. and S.C.O.G. acknowledge support from DFG via the Collaborative Research Center (SFB 881, Project-ID 138713538) “The Milky Way System” (subprojects A1, B1, B2 and B8) and from the Heidelberg Cluster of Excellence (EXC 2181 – 390900948) “STRUCTURES: A unifying approach to emergent phenomena in the physical world, mathematics, and complex dat”, funded by the German Excellence Strategy. They also thank for funding form the European Research Council in 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). F.B. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 726384/Empire) P.S.B. acknowledges support from grant PID2019-107427GB-C31 from the Spanish Ministry of Science and Innovation A.U. acknowledges support from the Spanish grants PGC2018-094671-B-I00, funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”, and PID2019-108765GB-I00, funded by MCIN/AEI/10.13039/501100011033. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018).
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