GRB091127/SN2009nz and the VLT/X-shooter spectroscopy of its host
  galaxy: probing the faint end of the mass-metallicity relation
  We perform a detailed study of the gamma-ray burst GRB091127/SN2009nz host
galaxy at z=0.490 using the VLT/X-shooter spectrograph in slit and
integral-field unit (IFU). 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 SN2009nz 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 are in agreement 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_star). Our results extend to lower M_star 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 2D velocity, velocity
dispersion and star formation rate (SFR) maps. They show that the host galaxy
has a perturbed rotation kinematics with evidence of a SFR enhancement
consistent with the afterglow position.
