Linking gas and galaxies at high redshift: MUSE surveys the environments
  of six damped Lyman alpha galaxies at z~3
  We present results from a survey of galaxies in the fields of six z>3 Damped
Lyman alpha systems (DLAs) using the Multi Unit Spectroscopic Explorer (MUSE)
at the Very Large Telescope (VLT). We report a high detection rate of up to
~80% of galaxies within 1000 km/s from DLAs and with impact parameters between
25 and 280 kpc. In particular, we discovered 5 high-confidence Lyman alpha
emitters associated with three DLAs, plus up to 9 additional detections across
five of the six fields. The majority of the detections are at relatively large
impact parameters (>50 kpc) with two detections being plausible host galaxies.
Among our detections, we report four galaxies associated with the most
metal-poor DLA in our sample (Z/Z_sun = -2.33), which trace an overdense
structure resembling a filament. By comparing our detections with predictions
from the Evolution and Assembly of GaLaxies and their Environments (EAGLE)
cosmological simulations and a semi-analytic model designed to reproduce the
observed bias of DLAs at z>2, we conclude that our observations are consistent
with a scenario in which a significant fraction of DLAs trace the neutral
regions within halos with a characteristic mass of 10^11-10^12 M_sun, in
agreement with the inference made from the large-scale clustering of DLAs. We
finally show how larger surveys targeting ~25 absorbers have the potential of
constraining the characteristic masses of halos hosting high-redshift DLAs with
sufficient accuracy to discriminate between different models.
