The high A_V Quasar Survey: A z=2.027 metal-rich damped Lyman-alpha
  absorber towards a red quasar at z=3.21
  To fully exploit the potential of quasars as probes of cosmic chemical
evolution and the internal gas dynamics of galaxies it is important to
understand the selection effects behind the quasar samples and in particular if
the selection criteria exclude foreground galaxies with certain properties
(most importantly a high dust content). Here we present spectroscopic follow-up
from the 10.4-m GTC telescope of a dust-reddened quasar, eHAQ0111+0641, from
the extended High A_V Quasar (HAQ) survey. We find that the z=3.21 quasar has a
foreground Damped Lyman-alpha Absorber (DLA) at z=2.027 along the line of
sight. The DLA has very strong metal lines due to a moderately high metallicity
(with an inferred lower limit of 25% of the solar metallicity), but a very
large gas column density along the line-of-sight in its host galaxy. This
discovery is further evidence that there is a dust bias affecting the census of
metals, caused by the combined effect of dust obscuration and reddening, in
existing samples of z>2 DLAs. The case of eHAQ0111+0641 illustrates that dust
bias is not only caused by dust obscuration, but also dust reddening.
