Star formation, structure and evolution of galaxies in loose groups: The environmental connection

Galaxies seldom live in isolation. Rather, they reside in multi-galaxy systems (clusters, loose groups, compact groups) spanning a large range in kinematical properties. This thesis investigates the relationship between environment and properties of galaxies belonging to loose groups. The galactic properties which we consider are morphology, near infrared colors, H{dollar}alpha{dollar} surface brightness (proportional to star formation rate), H{dollar}alpha{dollar} emission equivalent width (sensitive to the star formation history), color gradients, light distribution profiles, and luminosity functions.; Recent N-body simulations predict that transitory compact configurations, each typically consisting of {dollar}{lcub}sim{rcub}{dollar}2 to 5 galaxies, are created continuously during collapse of a loose group. Given this model, a loose group is expected to acquire an increasing number of merger remnants and peculiar galaxies as that group evolves dynamically. This thesis investigates the possible observational consequences of group evolution by comparing two samples of galaxy groups: (1) groups that contain galaxies listed in the Atlas of Peculiar Galaxies (Arp, 1966), which either have obvious disturbed morphologies and/or are likely to be involved in an interaction with a close neighboring group member(s), and (2) a control sample containing members having "normal" galaxy properties.; The thesis consists of 3 papers: the first paper (Chapter 2) describes observations and data analysis for the near infrared (JHK) imaging, taken with the Kitt Peak SQIID detector at the 1.3 meter telescope. Near infrared contours, aperture photometry, and results based on the near infrared colors are presented. The second paper (Chapter 3) provides a description of the data analysis for the R and H{dollar}alpha{dollar} CCD images, taken with the Case Western Reserve University Burrell Schmidt telescope at Kitt Peak. The morphology of the star forming regions are shown by displaying H{dollar}alpha{dollar} maps overlaid with R band contours. Near infrared H band and optical R band surface brightness profiles are compared, and general results from the survey are given. The third paper (Chapter 4) discusses the results from the surveys in the context of galaxy environment and group evolution.