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GRB 091127/SN 2009nz and the VLT/X-shooter spectroscopy of its host galaxy: probing the faint end of the mass-metallicity relation

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posted on 2012-10-24, 08:55 authored 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.



Astronomy & Astrophysics, 2011, 535


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