A Morphological Study of Gamma‐Ray Burst Host Galaxies

Abstract

We present a comprehensive study of the morphological properties of 42 γ-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 ∼ 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 ∼ −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.

A deep search for the host galaxies of gamma-ray bursts with no detected optical afterglow

“…Nevertheless, we conclude that the search for an interacting pair could be an effective means of finding GRB host galaxy candidates (see also Wainwright et al 2007;Chen 2012).…”

Connecting Gamma‐Ray Bursts and Galaxies: The Probability of Chance Coincidence1

“…In preSwift GRB samples, however, galaxies associated with GRBs have been noted to be a rather heterogeneous group (e.g., Conselice et al 2005;Le Floc'h et al 2003) covering a wide range of galaxy types and absolute magnitudes (M B $ À16 to À21; Sokolov et al 2001;Conselice et al 2005;Wainwright et al 2007), although there is a tendency for GRBs to occur in faint galaxies (Jaunsen et al 2003;Le Floc'h et al 2003;Fruchter et al 2006). Assuming a typical galaxy color of B À I ¼ 2 (Fukugita et al 1995), the brightest host galaxies could have I ¼ À23 and might be detected in our images to z $ 1.…”

“…As Swift (Gehrels et al 2004) accurately localizes hundreds of GRBs, statistical studies of GRB host galaxies are becoming increasingly critical to understanding GRB formation mechanisms (e.g., Christensen et al 2004;Wainwright et al 2007).…”

Spatially-resolved dust properties of the GRB 980425 host galaxy

“…Theoretically, rotating WR stars are the best candidates for long GRB progenitors, mainly because of their masses, angular momentum, and lack of the hydrogen envelope (Woosley 1993;Woosley & Heger 2006;Yoon & Langer 2005;Yoon et al 2006). However, the debate about whether the GRB rate is proportional to the star formation rate (SFR) density in the Universe is still ongoing (Conselice et al 2005;Castro Cerón et al 2006;Fruchter et al 2006;Stanek et al 2006;Wainwright et al 2007;Yüksel et al 2008;Fynbo et al 2009;Kistler et al 2009;Savaglio et al 2009;Leloudas et al 2010Leloudas et al , 2011Levesque et al 2010a,b;Svensson et al 2010;Elliott et al 2012;Michałowski et al 2012b;Robertson & Ellis 2012;Boissier et al 2013;Hao & Yuan 2013;Perley et al 2013).…”