S319p.158 — Early and late life – bulge-dominated cluster galaxies over the last 8-9 Gyr

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Aug 10th at 6:00 PM until 6:00 PM




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Author(s): Inger Jorgensen1, Kristin Chiboucas1, Marcel Bergmann1, Sune Toft3, Ricardo Schiavon2

Institution(s): 1. Gemini Observatory, 2. Liverpool John Moores University, 3. University of Copenhagen

We present results from the Gemini/HST Galaxy Cluster Project and its extension, which aims to map the evolution of bulge-dominated galaxies in rich clusters from redshift two to the present. Our high signal-to-noise spectra obtained with Gemini combined with HST imaging make it possible to study individual galaxies with masses as low as 1010.3 solar masses at redshift 1.3 (our current sample limit). In rich clusters out to z=1.3 we find no size evolution of the bulge-dominated galaxies. Further, the epoch of last star formation, as mapped by the M/L ratios, depends on the galaxy masses. At redshift 1.3 in the Lynx W cluster our data support a cluster-wide star formation episode only 1-2 Gyr prior, consistent with the epoch of last star formation epoch found from the M/L ratios. However, other aspects of our results question the simple picture of passive evolution of the bulge-dominated galaxies resulting in low redshift galaxies as observed in, e.g., the Coma cluster. Specifically, we find cluster-to-cluster variations in the metallicities and the abundance ratios of the galaxies. We are currently analyzing data of more clusters at redshifts 0.2-0.5 to investigate if such variations between clusters are common. Observations of additional clusters at z>1 are in progress.