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Astronomy Colloquium
The Invisibles: Revealing dark matter and the lower limit on galaxy Formation
Date: Tuesday, December 1st
Time: 3:30 pm - 5:00 pm
Place: 3425 Sterling Hall
Speaker: Beth Willman, Haverford College
Abstract: Tracking the growth of stellar mass in galaxies is a fundamental characterization of the galaxy population. Recent observations have shown that the total mass in L>L* red galaxies has increased by a factor of ~2 at z<1, although at different rates as a function of galaxy mass. Despite the advance made by these studies of the whole galaxy population, until recently it has not been clear if the growth of the red sequence depended on environment. Galaxy clusters are a useful probe of this as they sample the most extreme environments. However, progress toward answering this question has been hampered by a lack of deep multi-band imaging of a large sample of clusters that can be well linked to those in the local universe. To address this I will present the evolution of the red sequence as measured in 16 intermediate redshift clusters drawn from the ESO Distant Cluster Survey (EDisCS). Unlike massive x-ray selected clusters, these clusters have velocity dispersions that make them likely progenitors of clusters that populate the local Universe. I will show how the luminosity function (LF) of red-sequence galaxies in these clusters has evolved over 50% of cosmic time, highlighting the rapid buildup of the faint cluster galaxy population. I will also compare the evolution of the red sequence in clusters to the evolution of the field red sequence population and show that they evolve at different rates. Finally I will address how the total mass on the red sequence evolves in clusters and will use this to constrain the mechanisms of how red galaxies can be added to clusters. From this analysis it appears likely that some fraction of the light in recently added cluster red sequence galaxies is currently in the in the form of intracluster stars.
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