The host galaxy of GRB 031203: a new spectroscopic study
Universitá degli Studi di Milano-Bicocca, Dipartimento di Fisica, piazza della Scienza 3, 20126 Milano, Italy e-mail: firstname.lastname@example.org
2 INAF, Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (Lc), Italy
3 INAF, Osservatorio Astrofisico di Arcetri, largo E. Fermi 5, 50125 Firenze, Italy
4 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
5 INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00040, Monteporzio Catone (RM), Italy
6 ASI, Science Data Center, ASDC, c/o ESRIN, via G. Galilei, 00044 Frascati, Italy
7 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 København Ø, Denmark
Accepted: 21 August 2007
Aims.The host galaxy of the long-duration gamma-ray burst (GRB) 031203 (HG 031203) offers a precious opportunity to study in detail the environment of a nearby GRB. The aim is to better characterize this galaxy and analyse the possible evolution with time of the spectroscopic quantities we derive.
Methods.We analyse HG 031203 using a set of optical spectra acquired with the ESO-VLT and Keck telescope. We compare the metallicity, luminosity and star formation properties of this galaxy and of the other supernova-long gamma-ray burst hosts in the local universe () against the KPNO International Spectroscopic Survey.
Results. HG 031203 is a metal poor, actively star forming galaxy (star formation rate of 12.9±2.2 yr-1) at . From the emission-line analysis we derive an intrinsic reddening ≈ 0.4. This parameter doesn't show a compelling evidence of evolution at a month time-scale. We find an interstellar medium temperature of ≈ 12 500 K and an electronic density of = 160 cm-3. After investigating for possible Wolf-Rayet emission features in our spectra, we consider dubious the classification of HG 031203 as a Wolf-Rayet galaxy. Long gamma-ray burst (LGRB) and supernova hosts in the local universe () show, on average, specific star formation rates higher than ordinary star forming galaxy at the same redshift. On the other hand, we find that half of the hosts follows the metallicity–luminosity relation found for star-burst galaxies; HG 031203 is a clear outlier, with its really low metallicity (12+log(O/H) = 8.12±0.04).
Key words: gamma rays: bursts / galaxies: individual: GRB 031203 / ISM: abundances / stars: Wolf-Rayet
© ESO, 2007