GRB 091127/SN 2009nz and the VLT/X-shooter spectroscopy of its host galaxy: probing the faint end of the mass-metallicity relation
journal contributionposted on 24.10.2012, 08:55 by S. D. Vergani, H. Flores, S. Covino, D. Fugazza, J. Gorosabel, A. J. Levan, M. Puech, R. Salvaterra, J. C. Tello, A. D. U. Postigo, P. D'Avanzo, V. D'Elia, M. Fernandez, J. P. U. Fynbo, G. Ghirlanda, M. Jelinek, A. Lundgren, D. Malesani, E. Palazzi, S. Piranomonte, M. Rodrigues, R. Sanchez-Ramirez, V. Terron, C. C. Thoene, L. A. Antonelli, S. Campana, A. J. Castro-Tirado, P. Goldoni, F. Hammer, J. Hjorth, P. Jakobsson, L. Kaper, A. Melandri, B. Milvang-Jensen, J. Sollerman, G. Tagliaferri, N. R. Tanvir, K. Wiersema, R. A. M. J. Wijers
We perform a detailed study of the gamma-ray burst GRB 091127/SN 2009nz host galaxy at z = 0.490 using the VLT/X-shooter spectrograph in slit and integral-field unit (IFU) mode. From the analysis of the optical and X-ray afterglow data obtained from ground-based telescopes and Swift-XRT, we confirm the presence of a bump associated with SN 2009nz and find evidence of a possible jet break in the afterglow lightcurve. The X-shooter afterglow spectra reveal several emission lines from the underlying host, from which we derive its integrated properties. These properties agree with those of previously studied GRB-SN hosts and, more generally, with those of the long GRB host population. We use the Hubble Space Telescope and ground-based images of the host to determine its stellar mass (M⋆). Our results extend to lower M⋆ values the M-Z plot derived for the sample of long GRB hosts at 0.3 < z < 1.0 adding new information to probe the faint end of the M-Z relation and the shift of the LGRB host M-Z relation from that found from emission-line galaxy surveys. Thanks to the IFU spectroscopy, we can build the two-dimensional (2D) velocity, velocity dispersion, and star formation rate (SFR) maps. They show that the host galaxy has perturbed rotation kinematics with evidence of a SFR enhancement consistent with the afterglow position.