GRB 100219A with X-shooter - abundances in a galaxy at z = 4.7
  Abundances of galaxies at redshifts z > 4 are difficult to obtain from damped
Ly {\alpha} (DLA) systems in the sightlines of quasars (QSOs) due to the Ly
{\alpha} forest blanketing and the low number of high-redshift quasars
detected. Gamma-ray bursts (GRBs) with their higher luminosity are well suited
to study galaxies out to the formation of the first stars at z > 10. Its large
wavelength coverage makes the X-shooter spectrograph an excellent tool to study
the interstellar medium (ISM) of high redshift galaxies, in particular if the
redshift is not known beforehand. Here we determine the properties of a GRB
host at z = 4.66723 from a number of resonant low- and high ionization and
fine-structure absorption lines. This is one of the highest redshifts where a
detailed analysis with medium-resolution data has been possible. We detect one
intervening system at z = 2.18. The velocity components of the absorption lines
are fitted with Voigt-profiles and we determine a metallicity of [M/H] = -1.0
\pm 0.1 using S. The absorption lines show a complicated kinematic structure
which could point to a merger in progress. Si II* together with the restframe
UV energy release determined from GROND data gives us the distance of 0.3 to 1
kpc of the absorbing material from the GRB. We measure a low extinction of AV =
0.24 \pm 0.06 mag using X-ray spectral information and the flux calibrated
X-shooter spectrum. GRB-DLAs have a shallower evolution of metallicity with
redshift than QSO absorbers and no evolution in HI column density or ionization
fraction. GRB hosts at high redshift might continue the trend towards lower
metallicities in the LZ-relation with redshift, but the sample is still too
small to draw a definite conclusion. While the detection of GRBs at z > 4 with
current satellites is still difficult, they are very important for our
understanding of the early epochs of star- and galaxy-formation.
