Year: 2018
Type: article
Abstract: We estimate the star formation efficiency per gravitational free-fall time, , from observations of nearby galaxies with resolution matched to the typical size of a giant molecular cloud. This quantity, , 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 estimate . Assuming a constant thickness of the molecular gas layer ( H = 100 pc) across the whole sample, the median value of in our sample is 0.7%. We find a mild scale dependence, with higher measured at coarser resolution. Individual galaxies show different values of , with the median ranging from 0.3% to 2.6%. We find the highest 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.
Authors: Dyas Utomo, Jiayi Sun, Adam K. Leroy, J. M. Diederik Kruijssen, Eva Schinnerer, Andreas Schruba, Frank Bigiel, Guillermo A. Blanc, Mélanie Chevance, Eric Emsellem, Cinthya Herrera, Alexander P. S. Hygate, Kathryn Kreckel, Eve C. Ostriker, Jerome Pety, Miguel Querejeta, Erik Rosolowsky, Karin M. Sandstrom, Antonio Usero
Institutions: The Ohio State University, Heidelberg University, Max Planck Institute for Astronomy, Max Planck Institute for Extraterrestrial Physics, Carnegie Institution for Science, Carnegie Observatories, University of Chile, European Southern Observatory, Ausonius Institut de Recherche sur l'Antiquité et le Moyen age, Princeton University, Centre National de la Recherche Scientifique, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères, Spanish National Observatory, University of Alberta, University of California San Diego
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, National Aeronautics and Space Administration, National Radio Astronomy Observatory, International Max Planck Research School for Environmental, Cellular and Molecular Microbiology, European Commission, Deutsche Forschungsgemeinschaft, Universität Heidelberg, National Science Council, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, International Max Planck Research School for Advanced Methods in Process and Systems Engineering, Natural Sciences and Engineering Research Council of Canada, Comisión Nacional de Investigación Científica y Tecnológica, National Institutes of Natural Sciences, Astrophysics Division
Awards: G1380005828, G1406871949, G144508916, Collaborative Research: The Origin and Role of Dense Molecular Gas in Star-Forming Galaxies, G279537525, Star Formation at the Crossroads of Gravity and Turbulence, Collaborative Research: Dust, Gas, and Star Formation: Synthesizing 20 Years of Radio, Millimeter, and Infrared Surveys, On the Formation and Destruction of Giant Molecular Clouds in Galaxies, CAREER: Observing the Physics of Star Formation in Galaxies, G7225304350, G7390005016, G7809195351
OpenAlex ID: W2811192097