We present a comprehensive study of the morphological properties of 42 \gamma -ray burst ( GRB ) host galaxies imaged with the Hubble Space Telescope in the optical band .
The purpose of this study is to understand the relation of GRBs to their macro-environments , and to compare the GRB-selected galaxies to other high redshift samples .
We perform both qualitative and quantitative analyses by categorizing the galaxies according to their visual properties , and by examining their surface brightness profiles .
We find that all of the galaxies have approximately exponential profiles , indicative of galactic disks , and have a median scale length of about 1.7 kpc .
Inspection of the visual morphologies reveals a high fraction of merging and interacting systems , with \sim 30 \% showing clear signs of interaction , and an additional 30 \% exhibiting irregular and asymmetric structure which may be the result of recent mergers ; these fractions are independent of redshift and galaxy luminosity .
On the other hand , the three GRB host galaxies for which submillimeter and radio emission has been detected are isolated and compact , unlike the luminous submillimeter-selected galaxies .
The fraction of mergers appears to be elevated compared to other high redshift samples , particularly for the low luminosities of GRB hosts ( M _ { B } \sim - 16 to -21 mag ) .
This suggests that merging and interacting galaxies undergoing a burst of star formation may be an efficient site for the production of GRB progenitors .
Finally , we show that GRB hosts clearly follow the size-luminosity relation present in other galaxy samples , but thanks to absorption redshifts they help extend this relation to lower luminosities .