We present the stellar population properties of 69 short gamma-ray burst
(GRB) host galaxies, representing the largest uniformly-modeled sample to-date.
Using the Prospector stellar population inference code, we jointly fit
photometry and/or spectroscopy of each host galaxy. We find a population median
redshift of z=0.64β0.32+0.83β (68% confidence), including 10 new or
revised photometric redshifts at zβ³1. We further find a median
mass-weighted age of tmβ=0.8β0.53+2.71βGyr, stellar mass of
log(Mββ/Mββ)=9.69β0.65+0.75β, star formation rate of
SFR=1.44β1.35+9.37βMββyrβ1, stellar metallicity of
log(Zββ/Zββ)=β0.38β0.42+0.44β, and dust attenuation of
AVβ=0.43β0.36+0.85β~mag (68\% confidence). Overall, the majority of
short GRB hosts are star-forming (β84%), with small fractions that are
either transitioning (β6%) or quiescent (β10%); however, we
observe a much larger fraction (β40%) of quiescent and transitioning
hosts at zβ²0.25, commensurate with galaxy evolution. We find that
short GRB hosts populate the star-forming main sequence of normal field
galaxies, but do not include as many high-mass galaxies, implying that their
binary neutron star (BNS) merger progenitors are dependent on a combination of
host star formation and stellar mass. The distribution of ages and redshifts
implies a broad delay-time distribution, with a fast-merging channel at z>1
and a decreased BNS formation efficiency at lower redshifts. If short GRB hosts
are representative of BNS merger hosts within the horizon of current
gravitational wave detectors, these results can inform future searches for
electromagnetic counterparts. All of the data and modeling products are
available on the BRIGHT website.Comment: 32 pages, 15 figures, 3 tables, accepted to Ap