TY - JOUR
T1 - Star Formation Efficiency per Free-fall Time in nearby Galaxies
AU - Utomo, Dyas
AU - Sun, Jiayi
AU - Leroy, Adam K.
AU - Kruijssen, J. M.Diederik
AU - Schinnerer, Eva
AU - Schruba, Andreas
AU - Bigiel, Frank
AU - Blanc, Guillermo A.
AU - Chevance, Mélanie
AU - Emsellem, Eric
AU - Herrera, Cinthya
AU - Hygate, Alexander P.S.
AU - Kreckel, Kathryn
AU - Ostriker, Eve Charis
AU - Pety, Jerome
AU - Querejeta, Miguel
AU - Rosolowsky, Erik
AU - Sandstrom, Karin M.
AU - Usero, Antonio
N1 - Funding Information:
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.
Funding Information:
The work of D.U., A.K.L., and J.S. is partially supported by the National Science Foundation under grant Nos. 1615105, 1615109, and 1653300. J.M.D.K. and M.C. gratefully acknowledge funding from the German Research Foundation (DFG) in the form of an Emmy Noether Research Group (grant Number KR4801/1-1). J.M.D.K. gratefully acknowledges 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 No. 714907). E.S. acknowledges funding from the European Research Council (ERC) under the European Union‘s Horizon 2020 research and innovation program (grant agreement No. 694343). G.B. is supported by CONICYT/ FONDECYT, Programa de Iniciación, Folio 11150220. F.B. acknowledges funding from the European Union‘s Horizon 2020 research and innovation program (grant agreement No. 726384—EMPIRE). A.P.S.H. is a fellow of the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD). K.K. gratefully acknowledges support from grant KR 4598/1-2 from the DFG Priority Program 1573. The work of E.C.O. is supported by the NSF under grant No. 1713949. E.R. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number RGPIN-2017-03987. A.U. acknowledges support from Spanish MINECO grants ESP2015-68964 and AYA2016-79006. We acknowledge the usage of the Extragalactic Distance Database17 (Tully et al. 2009), the HyperLeda database18 (Makarov et al. 2014), the NASA/IPAC Extragalactic Database,19 and the SAO/NASA Astrophysics Data System.20
PY - 2018/7/10
Y1 - 2018/7/10
N2 - We estimate the star formation efficiency per gravitational free-fall time, ϵ ff , from observations of nearby galaxies with resolution matched to the typical size of a giant molecular cloud. This quantity, ϵ ff , is theoretically important but so far has only been measured for Milky Way clouds or inferred indirectly in a few other galaxies. Using new, high-resolution CO imaging from the Physics at High Angular Resolution in nearby Galaxies-Atacama Large Millimeter Array (PHANGS-ALMA) survey, we estimate the gravitational free-fall time at 60-120 pc resolution, and contrast this with the local molecular gas depletion time in order to estimateϵ ff . Assuming a constant thickness of the molecular gas layer (H = 100 pc) across the whole sample, the median value of ϵ ff in our sample is 0.7%. We find a mild scale dependence, with higherϵ ff measured at coarser resolution. Individual galaxies show different values of ϵ ff , with the median ϵ ff ranging from 0.3% to 2.6%. We find the highest ϵ ff in our lowest-mass targets, reflecting both long free-fall times and short depletion times, though we caution that both measurements are subject to biases in low-mass galaxies. We estimate the key systematic uncertainties, and show the dominant uncertainty to be the estimated line-of-sight (LOS) depth through the molecular gas layer and the choice of star formation tracers.
AB - We estimate the star formation efficiency per gravitational free-fall time, ϵ ff , from observations of nearby galaxies with resolution matched to the typical size of a giant molecular cloud. This quantity, ϵ ff , is theoretically important but so far has only been measured for Milky Way clouds or inferred indirectly in a few other galaxies. Using new, high-resolution CO imaging from the Physics at High Angular Resolution in nearby Galaxies-Atacama Large Millimeter Array (PHANGS-ALMA) survey, we estimate the gravitational free-fall time at 60-120 pc resolution, and contrast this with the local molecular gas depletion time in order to estimateϵ ff . Assuming a constant thickness of the molecular gas layer (H = 100 pc) across the whole sample, the median value of ϵ ff in our sample is 0.7%. We find a mild scale dependence, with higherϵ ff measured at coarser resolution. Individual galaxies show different values of ϵ ff , with the median ϵ ff ranging from 0.3% to 2.6%. We find the highest ϵ ff in our lowest-mass targets, reflecting both long free-fall times and short depletion times, though we caution that both measurements are subject to biases in low-mass galaxies. We estimate the key systematic uncertainties, and show the dominant uncertainty to be the estimated line-of-sight (LOS) depth through the molecular gas layer and the choice of star formation tracers.
KW - ISM: molecules
KW - galaxies: ISM
KW - galaxies: spiral
KW - galaxies: star formation
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U2 - 10.3847/2041-8213/aacf8f
DO - 10.3847/2041-8213/aacf8f
M3 - Article
AN - SCOPUS:85049940304
VL - 861
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
SN - 2041-8205
IS - 2
M1 - L18
ER -