Millimetric properties of gamma-ray burst host galaxies

R S Priddey,A S Fruchter,C Kouveliotou,I A Smith,R A M J Wijers,N R Tanvir,A J Levan

doi:10.1111/j.1365-2966.2006.10355.x

Abstract

We present millimetre (mm) and submillimetre (submm) photometry of a sample of five host galaxies of gamma-ray bursts (GRBs), obtained using the Max Planck Millimetre Bolometer (MAMBO2) array and Submillimetre Common-User Bolometer Array (SCUBA). These observations were obtained as part of an ongoing project to investigate the status of GRBs as indicators of star formation. Our targets include two of the most unusual GRB host galaxies, selected as likely candidate submm galaxies: the extremely red (R−K≈ 5) host of GRB 030115, and the extremely faint (R > 29.5) host of GRB 020124. Neither of these galaxies is detected, but the deep upper limits for GRB 030115 impose constraints on its spectral energy distribution, requiring a warmer dust temperature than is commonly adopted for submillimetre galaxies (SMGs). As a framework for interpreting these data, and for predicting the results of forthcoming submm surveys of Swift-derived host samples, we model the expected flux and redshift distributions based on luminosity functions of both submm galaxies and GRBs, assuming a direct proportionality between the GRB rate density and the global star formation rate density. We derive the effects of possible sources of uncertainty in these assumptions, including (1) introducing an anticorrelation between GRB rate and the global average metallicity, and (2) varying the dust temperature.

Highlights

There is strong evidence linking long-duration Gamma Ray Bursts (GRBs) with the core-collapse of massive stars (e.g. Hjorth et al 2003a)— and given the short mainsequence lifetimes of such stars, with star formation activity
The weighted mean 850μm flux of the sample discussed in Tanvir et al (2004) is 0.93±0.18, which could be interpreted as a true measure of the flux of the “typical” GRB host
In reality it is possible that the mean dust temperature of GRB hosts is different from the 37K assumed here, and that across the sample a distribution of temperatures is to be found

Summary

Introduction

There is strong evidence linking long-duration Gamma Ray Bursts (GRBs) with the core-collapse of massive stars (e.g. Hjorth et al 2003a)— and given the short mainsequence lifetimes of such stars, with star formation activity. The high luminosity of their prompt emission and afterglows enable them to be detected, in principle, out to redshifts 10 (in practice currently out to z > 6, e.g. Haislip et al 2006). Their high energy emission can pass unaffected through intervening gas and dust— the very conditions one would expect to be associated with massive star formation. Hitherto it has been difficult to assess the biases afflicting the assembly of such samples, factors modulating the GRB rate as a function of redshift (for example, redshift dependence of density of surrounding medium; metallicity; stellar initial mass function (IMF); the distribution of jet opening angles). The BAT (Burst Alert Telescope) detector is more sensitive to high-redshift bursts than previous missions (e.g. Band 2006), and, due to the rapid localisation of bursts via the onboard XRT (X-Ray Telescope), ground-based follow up of afterglows (yielding information constraining the physical properties of the afterglow, for example redshift, spectral slopes, light curves and jet-break times) is much more systematic

Methods

Results

Conclusion