The extremely red host galaxy of GRB 080207

TL;DR

This paper characterizes the host galaxy of dark GRB 080207 as an extremely red, dust-obscured galaxy with high star formation, evolved stellar populations, and significant dust extinction, at a redshift of about 2.2.

Contribution

It provides detailed multi-wavelength observations and analysis of a dark GRB host, revealing its nature as an ERO and DOG with high SFR and evolved stellar populations, a potentially distinct class of GRB hosts.

Findings

Host galaxy is an ERO and DOG with high dust extinction.

Photometric redshift determined as approximately 2.2.

Star formation rate estimated at about 119 solar masses per year.

Abstract

We present optical, near-infrared, and Spitzer IRAC and MIPS observations of the host galaxy of the dark gamma-ray burst GRB 080207. The host is faint, with extremely red optical-infrared colors ($R-K\,=\,6.3$, 24\micron/$R-$band flux $\sim1000$) making it an extremely red object (ERO) and a dust-obscured galaxy (DOG). The spectral energy distribution (SED) shows the clear signature of the 1.6 micron photometric "bump", typical of evolved stellar populations. We use this bump to establish the photometric redshift $z_{\rm phot}$ as 2.2$^{+0.2}_{-0.3}$, using a vast library of SED templates, including M 82. The star-formation rate (SFR) inferred from the SED fitting is $\sim$119\msun\,yr$^{-1}$, the stellar mass $3\times10^{11}$\,\msun, and \av\ extinction from 1-2\,mag. The ERO and DOG nature of the host galaxy of the dark GRB 080207 may be emblematic of a distinct class of dark GRB hosts, with high SFRs, evolved and metal-rich stellar populations, and significant dust extinction within the host galaxy.