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Revisiting the Integrated Star Formation Law. I. Non-starbursting Galaxies

de los Reyes, Mithi A. C. and Kennicutt, Robert C., Jr. (2019) Revisiting the Integrated Star Formation Law. I. Non-starbursting Galaxies. Astrophysical Journal, 872 (1). Art. No. 16. ISSN 1538-4357.

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We use new and updated gas- and dust-corrected star formation rate (SFR) surface densities to revisit the integrated star formation law for local "quiescent" spiral, dwarf, and low surface brightness galaxies. Using UV-based SFRs with individual IR-based dust corrections, we find that "normal" spiral galaxies alone define a tight Σ_(H I + H2)–Σ_(SFR) relation described by an n = 1.41^(+0.07)_(-0.07) power law with a dispersion of 0.28^(+0.02)_(-0.02) (errors reflect fitting and statistical uncertainties). The SFR surface densities are only weakly correlated with H I surface densities alone, exhibiting a stronger and roughly linear correlation with H2 surface densities, similar to what is seen in spatially resolved measurements of disks. However, many dwarf galaxies lie below the star formation law defined by spirals, suggesting a low-density threshold in the integrated star formation law. We consider alternative scaling laws that better describe both spirals and dwarfs. Our improved measurement precision also allows us to determine that much of the scatter in the star formation law is intrinsic, and we search for correlations between this intrinsic scatter and secondary physical parameters. We find that dwarf galaxies exhibit second-order correlations with the total gas fraction, stellar mass surface density, and dynamical time, which may explain much of the scatter in the star formation law. Finally, we discuss various systematic uncertainties that should be kept in mind when interpreting any study of the star formation law, particularly the X(CO) conversion factor and the diameter chosen to define the star-forming disk in a galaxy.

Item Type:Article
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URLURL TypeDescription Paper
de los Reyes, Mithi A. C.0000-0002-4739-046X
Additional Information:© 2019 The American Astronomical Society. Received 2018 October 15; revised 2018 December 14; accepted 2018 December 20; published 2019 February 6. This research made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research was supported in part by the STFC through a consolidated grant to the Institute of Astronomy, University of Cambridge. M.A. de los Reyes also acknowledges the financial support of the Winston Churchill Foundation and the NSF Graduate Research Fellowship Program. The authors would like to thank the anonymous referee for their thoughtful and constructive comments, as well as M. Irwin, A. Saintonge, L. Hunt, and J. Wang for their useful comments and advice. Finally, we would like to express our deep gratitude to the staff at academic and telescope facilities, particularly those whose communities are excluded from the academic system but whose labor maintains spaces for scientific inquiry. Software: Matplotlib (Hunter 2007), Linmix (Meyers 2015), Astropy (Astropy Collaboration et al. 2013).
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Winston Churchill FoundationUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:galaxies: dwarf – galaxies: spiral – galaxies: star formation
Record Number:CaltechAUTHORS:20190206-094805479
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Official Citation:Mithi A. C. de los Reyes and Robert C. Kennicutt Jr. 2019 ApJ 872 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92709
Deposited By: Tony Diaz
Deposited On:06 Feb 2019 18:18
Last Modified:17 Jun 2019 16:51

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