We present the first comprehensive analysis of Hubble Space Telescope ( HST ) observations of short-duration gamma-ray burst ( GRB ) host galaxies .
These observations allow us to characterize the galactic and local environments of short GRBs as a powerful constraint on the nature of their progenitors .
Using the HST data for 10 short GRB hosts we determine the host morphological properties , measure precise physical and host-normalized offsets relative to the galaxy centers , and study the locations of short GRBs relative to their host light distributions .
We find that most short GRB hosts have exponential disk profiles , characteristic of late-type galaxies , but with a median size that is twice as large as that of long GRB hosts , commensurate with their higher luminosities .
The observed distribution of projected physical offsets , supplemented by ground-based measurements , has a median of \approx 5 kpc , about 5 times larger than for long GRBs , and in good agreement with predicted offset distributions for NS-NS binary mergers .
For the short GRB population as a whole we find the following robust constraints : ( i ) \gtrsim 25 \% have projected offsets of \lesssim 10 kpc ; and ( ii ) \gtrsim 5 \% have projected offsets of \gtrsim 20 kpc .
We find no clear systematic trends for the offset distribution of short GRBs with and without extended soft emission .
While the physical offsets are larger than for long GRBs , the distribution of host-normalized offsets is nearly identical due to the larger size of short GRB hosts .
Finally , unlike long GRBs , which are concentrated in the brightest regions of their host galaxies , short GRBs appear to under-represent the light distribution of their hosts ; this is true even in comparison to core-collapse and Type Ia supernovae .
Based on these results , we conclude that short GRBs are consistent with a progenitor population of NS-NS binaries , but partial contribution from prompt or delayed magnetar formation is also consistent with the data .
Our study underscores the importance of future HST observations of the larger existing and growing sample of short GRB hosts , which will allow us to delineate the properties of the progenitor population .