Low-ionization galaxies and evolution in a pilot survey up to z = 1

Abstract

We present galaxy spectroscopic data on a pencil beam of $10.75^{\prime }\times 7.5^{\prime }$ 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 $\mathrm{R}\le 23$, 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], $\mathrm{H}\beta$, 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 $z\sim 0.6-0.7$, 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 $z\sim 0.8$, 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 $0.35\le z\le 0.65$ we find that 23% of the early-type galaxies have LINER-like spectra with $\mathrm{H}\beta$ 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.

26 pages, ; Accepted for publication in Research in Astronomy and Astrophysics

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Cited by in corpus (2)

• Intergalactic stellar populations in intermediate redshift clusters
• Diffuse Intracluster Light at Intermediate Redshifts: ICL observations in a X-ray cluster at z=0.29