Star Formation Laws and Efficiencies across 80 Nearby Galaxies

Sun, Jiayi and Leroy, Adam K. and Ostriker, Eve C. and Meidt, Sharon and Rosolowsky, Erik and Schinnerer, Eva and Wilson, Christine D. and Utomo, Dyas and Belfiore, Francesco and Blanc, Guillermo A. and Emsellem, Eric and Faesi, Christopher and Groves, Brent and Hughes, Annie and Koch, Eric W. and Kreckel, Kathryn and Liu, Daizhong and Pan, Hsi-An and Pety, Jérôme and Querejeta, Miguel and Razza, Alessandro and Saito, Toshiki and Sardone, Amy and Usero, Antonio and Williams, Thomas G. and Bigiel, Frank and Bolatto, Alberto D. and Chevance, Mélanie and Dale, Daniel A. and Gensior, Jindra and Glover, Simon C. O. and Grasha, Kathryn and Henshaw, Jonathan D. and Jiménez-Donaire, María J. and Klessen, Ralf S. and Kruijssen, J. M. Diederik and Murphy, Eric J. and Neumann, Lukas and Teng, Yu-Hsuan and Thilker, David A. (2023) Star Formation Laws and Efficiencies across 80 Nearby Galaxies. The Astrophysical Journal Letters, 945 (2). L19. ISSN 2041-8205

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We measure empirical relationships between the local star formation rate (SFR) and properties of the star-forming molecular gas on 1.5 kpc scales across 80 nearby galaxies. These relationships, commonly referred to as "star formation laws," aim at predicting the local SFR surface density from various combinations of molecular gas surface density, galactic orbital time, molecular cloud free fall time, and the interstellar medium dynamical equilibrium pressure. Leveraging a multiwavelength database built for the Physics at High Angular Resolution in Nearby Galaxies (PHANGS) survey, we measure these quantities consistently across all galaxies and quantify systematic uncertainties stemming from choices of SFR calibrations and the CO-to-H2 conversion factors. The star formation laws we examine show 0.3–0.4 dex of intrinsic scatter, among which the molecular Kennicutt–Schmidt relation shows a ∼10% larger scatter than the other three. The slope of this relation ranges β ≈ 0.9–1.2, implying that the molecular gas depletion time remains roughly constant across the environments probed in our sample. The other relations have shallower slopes (β ≈ 0.6–1.0), suggesting that the star formation efficiency per orbital time, the star formation efficiency per free fall time, and the pressure-to-SFR surface density ratio (i.e., the feedback yield) vary systematically with local molecular gas and SFR surface densities. Last but not least, the shapes of the star formation laws depend sensitively on methodological choices. Different choices of SFR calibrations can introduce systematic uncertainties of at least 10%–15% in the star formation law slopes and 0.15–0.25 dex in their normalization, while the CO-to-H2 conversion factors can additionally produce uncertainties of 20%–25% for the slope and 0.10–0.20 dex for the normalization.

Item Type: Article
Subjects: Eprints STM archive > Physics and Astronomy
Depositing User: Unnamed user with email admin@eprints.stmarchive
Date Deposited: 29 Apr 2023 07:48
Last Modified: 30 Dec 2023 13:19

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