Low-ionization galaxies and evolution in a pilot survey up to z = 1
  We present galaxy spectroscopic data on a pencil beam of $10.75' \times7.5'$
centered on the X-ray cluster RXJ0054.0-2823 at $z = 0.29$. We study the
spectral evolution of galaxies from $z=1$ down to the cluster redshift in a
magnitude-limited sample at $\rm R\leq23$, for which the statistical properties
of the sample are well understood. We divide emission-line galaxies in
star-forming galaxies, LINERs, and Seyferts by using emission-line ratios of
[OII], $\rm H\beta$, and [OIII], and derive stellar fractions from population
synthesis models. We focus our analysis on absorption and low-ionization
galaxies. For absorption-line galaxies we recover the well known result that
these galaxies have had no detectable evolution since $z\sim0.6-0.7$, but we
also find that in the range $z=0.65-1$ at least 50% of the stars in bright
absorption systems are younger than 2.5Gyr. Faint absorption-line galaxies in
the cluster at $z = 0.29$ also had significant star formation during the
previous 2-3Gyr, while their brighter counterparts seem to be composed only of
old stars. At $z\sim0.8$, our dynamically young cluster had a truncated
red-sequence. This result seems to be consistent with a scenario where the
final assembly of E/S0 took place at $z<1$. In the volume-limited range
$0.35\leq z\leq0.65$ we find that 23% of the early-type galaxies have
LINER-like spectra with $\rm H\beta$ in absorption and a significant component
of A stars. The vast majority of LINERs in our sample have significant
populations of young and intermediate-aged stars and are thus not related to
AGN, but to the population of `retired galaxies' recently identified by
Cid-Fernandes et al. (2010) in the SDSS. Early-type LINERs with various
fractions of A stars, and E+A galaxies appear to play an important role in the
formation of the red sequence.
