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N.A. Miller (NASA/GSFC)
Galaxy evolution in the cluster environment was investigated through a sample of over 400 active galaxies drawn from 20 nearby Abell clusters. The active galaxies were identified via radio continuum emission, and follow-up optical spectroscopy provided confirmation of cluster memberships and characterization of the galaxies.
A population of galaxies with large nuclear dust extinction was identified. Bluer emission features in such spectra are lost, yet their radio, FIR, and H-alpha properties identify them as star-forming galaxies. In some cases, the blue spectra of such galaxies even appear to be post-starburst. The radial distribution of this dusty star-forming population strongly suggests that it is related to some aspect of the cluster environment.
Comparison of the properties of individual clusters revealed variation in their active populations. This variation was most apparent when assessed in light of both radio and optical properties. Specifically, a significant excess of optically-faint star-forming galaxies was identified in Abell 2255. This appears to be related to the cluster's dynamical state, as it is an excellent example of a cluster-cluster merger. However, the active populations in other merger candidates differed, suggesting that an additional parameter such as merger stage is needed to understand the relationship.
This dissertation research was performed while the author was a predoctoral associate at the National Radio Astronomy Observatory in Socorro, New Mexico.
The author(s) of this abstract have provided an email address for comments about the abstract: nmiller@stis.gsfc.nasa.gov