We present a comprehensive optical and near-infrared census of the fields of 90 short gamma-ray bursts (GRBs) discovered in 2005-2021, constituting all short GRBs for which host galaxy associations are feasible (≈ 60% of the total Swift short GRB population). We contribute 245 new multi-band imaging observations across 49 distinct GRBs and 25 spectra of their host galaxies. Supplemented by literature and archival survey data, the catalog contains 335 photometric and 40 spectroscopic data sets. The photometric catalog reaches 3σ depths of ≳24−27 mag and ≳23−26 mag for the optical and near-infrared bands, respectively. We identify host galaxies for 84 bursts, in which the most robust associations make up 54% (49/90) of events, while only a small fraction, 6.7%, have inconclusive host associations. Based on new spectroscopy, we determine 17 host spectroscopic redshifts with a range of z≈0.15−1.6 and find that ≈ 25-44% of Swift short GRBs originate from z>1. We also present the galactocentric offset catalog for 83 short GRBs. Taking into account the large range of individual measurement uncertainties, we find a median of projected offset of ≈7.9 kpc, for which the bursts with the most robust associations have a smaller median of ≈4.9 kpc. Our catalog captures more high-redshift and low-luminosity hosts, and more highly-offset bursts than previously found, thereby diversifying the population of known short GRB hosts and properties. In terms of locations and host luminosities, the populations of short GRBs with and without detectable extended emission are statistically indistinguishable. This suggests that they arise from the same progenitors, or from multiple progenitors which form and evolve in similar environments. All of the data products are available on the BRIGHT website.

We present the stellar population properties of 68 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 the photometry and/or spectroscopy of each host galaxy. We find a population median redshift of z=0.60+0.90−0.34 (68% confidence), including 10 new or revised photometric redshifts at z≳1. We further find a median mass-weighted age of tm=0.85+2.49−0.57 Gyr, a stellar mass of log(M∗/M⊙)=9.69+0.95−0.66, a star formation rate of SFR=1.46+10.55−1.38M⊙/yr, a stellar metallicity of log(Z∗/Z⊙)=−0.4+0.46−0.42, and a dust attenuation of AV=0.51+0.94−0.43 mag (68% confidence). Overall, the majority of short GRB hosts are star-forming (≈85%), with small fractions that are either transitioning (≈6%) or quiescent (≈9%); however, we observe a much larger fraction (≈60%) of quiescent and transitioning hosts at z≲0.25, 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. Moreover, we find that short GRBs originate in environments with a wide range of stellar metallicities. 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.