leaf Home               books   UofT Astronomy and Astrophysics Theses List

An Infrared Study of Distant Galaxy Clusters

Adam Virgil Muzzin

Doctor of Philosophy 2008
Graduate Department of Astronomy and Astrophysics, University of Toronto

We present a study of the infrared properties distant galaxy clusters and their constituent galaxies covering the wavelength range 2.2 μm - 24 μm. In the first part of the thesis we use ground-based K-band (2.2μm) data to study the scaling relations and luminosity functions (LFs) of 15 moderate redshift (0.2 < z < 0.5), X-ray luminous galaxy clusters. We find that the IR-selected density profiles, IR LFs, and the IR richness/ light vs. mass scaling relations for these clusters are nearly identical to their local (z < 0.1) counterparts. The only notable change in the cluster NIR properties with redshift is the shallowing of the faint-end slope of the early-type LF with increasing redshift, which is attributed to "downsizing" in the cluster population.

In the second part of the thesis we combine the R-band and [3.6μm] photometry from the 3.8 deg2 Spitzer First Look Survey and use the cluster red-sequence method to discover a set of 99 clusters at 0.1 < z < 1.3. Using this cluster sample we make the first measurement of the suite of IRAC cluster LFs ([3.6μm], [4.5μm], [5.8μm], [8.0μm]) from 0.1 < z < 1.0. Similar to the K-band study we find that for the bands that trace stellar mass at these redshifts ([3.6μm], [4.5μm]) the evolution in M* is consistent with a passively evolving population of galaxies with a high formation redshift (z f > 1.5). The MIR ([5.8μm] & [8.0μm]) cluster LFs show that at z < 0.4 the bright-end of the cluster LF is well-described by a composite population of quiescent galaxies and regular star forming galaxies with a mix consistent with typical cluster blue fractions; however, at z > 0.4, an additional population of dusty starburst galaxies is required to properly model these LFs.

In the final part of the thesis we present the results of a spectroscopic survey of cluster galaxies detected at 24μm. We use the optical spectroscopy to classify the galaxies and find that the majority of cluster MIR galaxies are star forming galaxies (~ 80%), although their specific classes make them a very heterogeneous subset of galaxies. By comparing the equivalent widths of nebular emission lines we show that there is a non-negligible population of dusty star forming galaxies in clusters which have optical - IR colors redder than the cluster red-sequence.

Reproduced with permission. library@astro.utoronto.ca
November 20 2007