Probing dust-obscured star formation in the most massive gamma-ray burst host galaxies^⋆

¹ Max-Planck-Institut für extraterrestrische Physik, 85740 Garching, Giessenbachstr. 1, Germany
e-mail: jcg@mpe.mpg.de
² Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3hJ, UK
³ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
⁴ INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, 9000 Gent, Belgium
⁶ Department of Physics and Astrophysics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
⁷ CSIRO Astronomy & Space Science, Australia Telescope National Facility, PO Box 76, 1710 Epping, Australia
⁸ National Centre for Radio Astrophysics, TIFR, Ganeshkind, 411007 Pune, India
⁹ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía, s/n, 18008 Granada, Spain
¹⁰ CSIRO Astronomy & Space Science, Locked Bag 194, 2390 Narrabri, Australia
¹¹ Astrophysics Data System, Harvard-Smithonian Center for Astrophysics, Garden St. 60, Cambridge, MA 02138, USA
¹² Universidad de Valparaıso, Instituto de Física y Astronomía, Gran Bretana 1111, Valparaıso, Chile
¹³ INAF, Institute of Space Astrophysics and Cosmic Physics, via P. Gobetti 101, 40129 Bologna, Italy
¹⁴ Physics Dept., University of Calabria, via P. Bucci, 87036 Arcavacata di Rende, Italy

Received: 5 May 2016
Accepted: 24 June 2016

Abstract

Context. As a result of their relation to massive stars, long-duration gamma-ray bursts (GRBs) allow the pinpointing of star formation in galaxies independent of redshift, dust obscuration, or galaxy mass/size, thus providing a unique tool to investigate star formation history over cosmic time.

Aims. About half of the optical afterglows of long-duration GRBs are missed owing to dust extinction and are primarily located in the most massive GRB hosts. It is important to investigate the amount of obscured star formation in these GRB host galaxies to understand this bias.

Methods. Radio emission of galaxies correlates with star formation, but does not suffer extinction as do the optical star formation estimators. We selected 11 GRB host galaxies with either large stellar mass or large UV-based and optical-based star formation rates (SFRs) and obtained radio observations of these with the Australia Telescope Compact Array and the Karl Jansky Very Large Array.

Results. Despite intentionally selecting GRB hosts with expected high SFRs, we do not find any radio emission related to star formation in any of our targets. Our upper limit for GRB 100621A implies that the earlier reported radio detection was due to afterglow emission. We detect radio emission from the position of GRB 020819B, but argue that it is in large part, if not completely, due to afterglow contamination.

Conclusions. Half of our sample has radio-derived SFR limits, which are only a factor 2–3 above the optically measured SFRs. This supports other recent studies that the majority of star formation in GRB hosts is not obscured by dust.