The host galaxy of the short GRB 111117A at z = 2.211

Abstract

It is notoriously difficult to localize short γ-ray bursts (sGRBs) and their hosts to measure their redshifts. These measurements, however, are critical for constraining the nature of sGRB progenitors, their redshift distribution, and the r-process element enrichment history of the universe. Here we present spectroscopy of the host galaxy of GRB 111117A and measure its redshift to be z = 2.211. This makes GRB 111117A the most distant high-confidence short duration GRB detected to date. Our spectroscopic redshift supersedes a lower, previously estimated photometric redshift value for this burst. We use the spectroscopic redshift, as well as new imaging data to constrain the nature of the host galaxy and the physical parameters of the GRB. The rest-frame X-ray derived hydrogen column density, for example, is the highest compared to a complete sample of sGRBs and seems to follow the evolution with redshift as traced by the hosts of long GRBs. From the detection of Lyα emission in the spectrum, we are able to constrain the escape fraction of Lyα in the host. The host lies in the brighter end of the expected sGRB host brightness distribution at z = 2.211, and is actively forming stars. Using the observed sGRB host luminosity distribution, we find that between 43% and 71% of all Swift-detected sGRBs have hosts that are too faint at z ~ 2 to allow for a secure redshift determination. This implies that the measured sGRB redshift distribution could be incomplete at high redshift. The high z of GRB 111117A is evidence against a lognormal delay-time model for sGRBs through the predicted redshift distribution of sGRBs, which is very sensitive to high-z sGRBs. From the age of the universe at the time of GRB explosion, an initial neutron star (NS) separation of a0 < 3.1 R⊙ is required in the case where the progenitor system is a circular pair of inspiralling NSs. This constraint excludes some of the longest sGRB formation channels for this burst.

A comparison between short GRB afterglows and kilonova AT2017gfo: shedding light on kilonovae properties

“…A2). Finally, we have updated the redshift of GRB 111117A with the more refined measure of z=2.211 (Selsing et al 2018). Note that, contrary to Gompertz et al (2018), we decided to not include GRB 051210 because, according to the most recent literature, only a lower limit on the redshift exists (z > 1.4, see Berger et al 2007;Fong et al 2015).…”

“…GRB 060614 (Price et al 2006); GRB 100816A (Tanvir et al 2010); GRB 150423A (Selsing et al 2019); GRB 150424A (Castro-Tirado et al 2015); GRB 160410A (Selsing et al 2019); GRB 160624A (Cucchiara & Levan 2016); GRB 160821B ; GRB 170428A (Izzo et al 2017). c new redshift from Selsing et al (2018). d Not well defined redshift (see § 2.3).…”

NGC 4993 and other short gamma-ray burst host galaxies

“…2.3.5. GRB 111117A host SED (Selsing et al 2018) Selsing et al (2018 presented spectroscopy and photometry data of the GRB 111117A host galaxy with an estimated redshift of z = 2.211. The galaxy is actively forming stars.…”

“…For SGRB 051221a the photometric data are too few to be used to model the SED. SED of GRB 111117A host fromSelsing et al (2018). Open circles: the data; dashed line: bb flux corresponding to T bb = 8000 K.…”

Discovery of the Optical Afterglow and Host Galaxy of Short GRB 181123B at z = 1.754: Implications for Delay Time Distributions

“…However, to date, only ≈5% of bursts have confirmed redshifts of z>1. This drops to ≈1.5% (two events) when considering the confirmed secure SGRBs at z>1.5: GRB 111117A at z=2.211 (Selsing et al 2018) and GRB 160410A at z=1.717 (Selsing et al 2016). 19 In general, high-redshift SGRBs are particularly challenging to characterize for a number of reasons.…”