The Nature and Evolution of Infrared Galaxies in Clusters

In chapter 1, I present a spectroscopic and photometric study of 105 Spitzer-MIPS 24 micron detected galaxies in the fields of candidate clusters from the SpARCS survey. I spectroscopically both confirm nine clusters of galaxies at 0.07 < z < 0.49 and investigate the nature of the cluster members and field galaxies to compare their optical and infrared star formation activities. Spectroscopic classifications reveal different populations of galaxies in clusters and in the field. Most 24 micron sources are star forming galaxies which are mostly dusty starbursts. I conclude that specific star formation rates of star forming galaxies in clusters are not dependent upon clustercentric radius, but, rather, dependent upon stellar mass.In chapter 2, I present the results of an infrared study of 250 galaxy clusters at 0.2 < z < 1 from the SpARCS survey. My sample spans a cluster mass range 14 < log M_sun < 15 with an average about 2x10^14 M_sun over the redshift. Assuming a star forming galaxy template, I statistically count the number of infrared luminous galaxies in clusters above a fixed inferred infrared luminosity of 6x10^11 L_sun per unit cluster mass and find it increases with redshift. Fitting a simple power law, I measure an evolution of (1 + z )^(5.2±0.5) within R_200 and (1 + z )^(9.6±1.6) within R = 2Mpc from the cluster center over the redshift range of this sample. By accounting for the evolution of infrared galaxies in the field, I show that this observed evolution in clusters is due to new infalling field galaxies. Also, I estimate the total star formation rate per unit cluster mass (SFR/M_cluster) and find a similar evolution of (1+z)^(5.6±0.5) within R_(200) and (1+z)^(8.6±1.5) within R = 2Mpc from the cluster center. The surface density of the infrared luminous galaxies seems to decrease as the distance from cluster center increases. Finally, I show that the accretion rate of infalling infrared galaxies from the field into clusters increases at higher redshifts.In chapter 3, I investigate the position of MORPHS spectral types of galaxies at z < 0.5 on an IRAC color-color diagram. My sample includes 57 members from a galaxy cluster (SpARCS J104101+581741) at z = 0.0726 and 26 members from three other clusters at z = 0.288, 0.353 and 0.487 along with 24 galaxies in the field. I find that the IRAC color-color diagram isolates QSOs, poststarbursts, and passive galaxies very well but it is unable to distinguish between pure star forming and AGN galaxies because of the complexity of PAH emission lines in their spectra. At lower redshifts, I observe an evolutionary sequence of star forming galaxies from passive to starburst galaxies