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# The properties of galaxies in supercluster filaments

Porter, Scott Clive (2007)
Ph.D. thesis, University of Birmingham.

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## Abstract

Superclusters appear as large-scale structures in the form of a network of filaments, and can be up to 100h$$^{-1}_{100}$$ Mpc in extent. In this dissertation, we investigate in detail the spatial structure of the three richest superclusters of galaxies closer to us then z=0.1. We investigate the rate of star formation in galaxies at various positions among the filaments and clusters in the Pisces-Cetus Supercluster. We use an index of star formation derived from a principal component analysis of optical spectral. We have shown that galaxies which are members of these filaments, show a steady decline in star formation rate, from the periphery of a cluster, into the cluster core. However, on top of this trend, we find a nearby instantaneous enhancement of the rate of star formation at ~3h$$^{-1}_{70}$$ Mpc from its centre. We conclude that the most likely reason for this sudden enhancement in star formation rate is galaxy-galaxy harassment. Further work shows that the enhancement in star formation occurs mainly in the in falling dwarf galaxies (-20 < MB < -17.5) and that there is little evidence that the tidal effect of the dark matter haloes of the clusters is responsible for the enhanced star formation. The results of an analysis performed on a larger ensemble of 52 filaments were consistent with those from our smaller sample drawn from the Pisces-Cetus supercluster. We conclude this study with the analysis of a sample of spectra from the 6dF redshift survey. In the absence of spectrophotometric calibration, for these galaxies we were only able to obtain an uncalibrated star formation rate, but we could examine the effect of correction due to dust extinction, and could separate the starforming galaxies from the active galactic nuclei. From our small sample, there was interesting evidence of enhanced star formation in galaxies at similar distances from the centres of the clusters in the Shapley Supercluster.

Type of Work: Ph.D. thesis. Raychaudhury, Somak Schools (1998 to 2008) > School of Physics & Astronomy Astrophysics and Space Research Group Galaxies: clusters: general; Galaxies: evolution; large-scale structure of the Universe; cosmology: observations; Galaxies: starburst; X-rays. QB Astronomy University of Birmingham Check for printed version of this thesis 986
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