Galaxies in the Early Universe characterized in absorption and emission
  Understanding how galaxies evolved from the early Universe through cosmic
time is a fundamental part of modern astrophysics. In order to study this
evolution it is important to sample the galaxies at various times in a
consistent way through time. In regular luminosity selected samples, our
analyses are biased towards the brightest galaxies at all times (as these are
easier to observe and identify). A complementary method relies on the
absorption imprint from neutral gas in galaxies, the so-called damped Ly-alpha
absorbers (DLAs) seen towards distant bright objects. This thesis seeks to
understand how the absorption selected galaxies relate to the emission selected
galaxies by identifying the faint glow from the absorbing galaxies at redshift
z~2.
  In the last Chapter, a study of the more evolved, massive galaxies is
presented. These galaxies are observed to be a factor of 2 to 6 times smaller
than local galaxies of similar masses. A new spectroscopically selected sample
is presented and the increased precision of the redshifts allows a more
detailed measurement of the scatter in the mass-size relation. The size
evolution of massive, quiescent galaxies is modelled by a `dilution' scenario,
in which progressively larger galaxies at later times are added to the
population of denser galaxies, causing an increase of the mean size of the
population. This model describes the evolution of both sizes and number
densities very well, however, the scatter in the model increases with time,
contrary to the data. It is thus concluded that a combination of `dilution' and
individual growth, e.g., through mergers, is needed.
  For brevity, the individual chapters based on published peer-reviewed
articles are omitted and a link to the given article is given instead.
  Principal supervisor: Johan P. U. Fynbo
