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Physical Sciences and Mathematics Commons

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Astrophysics and Astronomy

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University of Massachusetts Amherst

2012

Cosmology: observations

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Full-Text Articles in Physical Sciences and Mathematics

The Assembly Of Galaxies Over Cosmic Time, Yicheng Guo Sep 2012

The Assembly Of Galaxies Over Cosmic Time, Yicheng Guo

Open Access Dissertations

To Understand how galaxies were assembled across the cosmic time remains one of the most outstanding questions in astronomy. The core of this question is how today's Hubble Sequence, namely the differentiation of galaxy morphology and its correlation to galaxy physical properties, is formed. In this thesis, we investigate the origin of the Hubble Sequence through galaxies at z~2, an epoch when the cosmic star formation activity reaches its peak and the properties of galaxies undergo dramatic transitions. Galaxies at z~2 have two important features that are distinct from nearby galaxies: much higher frequency of clumpy morphology in star-forming systems, …


Evidence For Significant Growth In The Stellar Mass Of Brightest Cluster Galaxies Over The Past 10 Billion Years, C. Lidman, J. Suherli, A. Muzzin, Grant Wilson, R. Demarco, S. Brough, A. Rettura, J. Cox, A. Degroot, H. K. C. Yee, D. Gilbank, H. Hoekstra, M. Balogh, E. Ellingson, A. Hicks, J. Nantais, A. Noble, M. Lacy, J. Surace Jan 2012

Evidence For Significant Growth In The Stellar Mass Of Brightest Cluster Galaxies Over The Past 10 Billion Years, C. Lidman, J. Suherli, A. Muzzin, Grant Wilson, R. Demarco, S. Brough, A. Rettura, J. Cox, A. Degroot, H. K. C. Yee, D. Gilbank, H. Hoekstra, M. Balogh, E. Ellingson, A. Hicks, J. Nantais, A. Noble, M. Lacy, J. Surace

Grant Wilson

Using new and published data, we construct a sample of 160 brightest cluster galaxies (BCGs) spanning the redshift interval 0.03 < z < 1.63. We use this sample, which covers 70% of the history of the universe, to measure the growth in the stellar mass of BCGs after correcting for the correlation between the stellar mass of the BCG and the mass of the cluster in which it lives. We find that the stellar mass of BCGs increase by a factor of 1.8 between z=0.9 and z=0.2. Compared to earlier works, our result is closer to the predictions of semi-analytic models. However, BCGs at z=0.9, relative to BCGs at z=0.2, are still a factor of 1.5 more massive than the predictions of these models. Star formation rates in BCGs at z~1 are generally to low to result in significant amounts of mass. Instead, it is likely that most of the mass build up occurs through mainly dry mergers in which perhaps half of the mass is lost to the intra-cluster medium of the cluster.