The Star Formation Rate–Radius Connection: Data and Implications for Wind Strength and Halo Concentration

The Astrophysical Journal, vol. 899, pp. 93

Abstract

Abstract This paper is one in a series that explores the importance of radius as a second parameter in galaxy evolution. The topic investigated here is the relationship between star formation rate (SFR) and galaxy radius ( ) for main-sequence star-forming galaxies. The key observational result is that, over a wide range of stellar mass and redshift in both CANDELS and SDSS, there is little correlation between SFR and at fixed stellar mass. The Kennicutt–Schmidt law, or any similar density-related star formation law, then implies that smaller galaxies must have lower gas fractions than larger galaxies (at fixed ), and this is supported by observations of gas in local star-forming galaxies. We investigate the implications by adopting the equilibrium “bathtub” model: the ISM gas mass is assumed to be constant over time, and the net SFR is the difference between the accretion rate of gas onto the galaxy from the halo and the outflow rate due to winds. To match the observed null correlation between SFR and radius, the bathtub model requires that smaller galaxies at fixed mass have weaker galactic winds. Our hypothesis is that galaxies are a two-parameter family whose properties are set mainly by halo mass and concentration. These determine the radius and gas accretion rate, which in turn predict how wind strength needs to vary with to keep the SFR constant.

Authors 3

1. Arjen van der Wel

   Ghent University · Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg, Germany

   Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium

2. Avishai Dekel

   University of California, Santa Cruz · Hebrew University of Jerusalem

   Affiliation as printed

   Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel

   SCIPP, University of California, Santa Cruz, CA 95064, USA

3. Anton M. Koekemoer

   Space Telescope Science Institute

   Affiliation as printed

   Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA