The Offset and Host Light Distributions of Long Gamma-Ray Bursts: A New View from HST Observations of Swift Bursts

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[Abridged] We present the results of an extensive Hubble Space Telescope (HST) imaging study of ~100 Swift long-duration gamma-ray bursts (LGRBs) spanning 0.03 < z < 9.4 using relative astrometry from afterglow observations to locate the bursts within their host galaxies.

• We measure the distribution of LGRB offsets from their host centers, as well as their relation to the underlying host light distribution.
• We find that the host-normalized offsets (R/R_h) of LGRBs are more centrally concentrated than expected for an exponential disk profile, with a median of 0.67, and in particular they are more concentrated than the underlying surface brightness profiles of their host galaxies.
• The distribution of offsets is inconsistent with the distribution for Type II supernovae (SNe) but consistent with the distribution for Type Ib/c SNe.