Environmental effects on dwarf galaxy evolution

Using an N-body/Tree-code and Smoothed Particle Hydrodynamics, the influence of ram pressure stripping and harassment on an infalling star-forming galaxy population is investigated. In combination these mechanisms act to strip late-type dwarfs of their gas content in less than 0.5 Gyrs, causing a cessation of star-formation. As a result, late-type dwarfs evolve to colours typical of cluster dwarf ellipticals in less than 2 Gyrs, although the period in which they would be classified as transition objects lasts less than 1 Gyr. The rapid removal of a significant fraction of the dwarfs disk mass by ram pressure stripping causes morphological transformation of the stellar component, producing rotation-to-dispersion ratios in agreement with observations of cluster dwarf ellipticals. A Monte-Carlo simulation is utilised to quantify the effects of harassment, and strong, disruptive tidal encounters are found to be rare. The typical observable con sequences of harassment are found to be minor, producing very low surface brightness features (visible at surface brightnesses limits of > 30/j,b arcsec 2), and a reduction in dynamical mass-to-light ratios by roughly a factor of 2. The influence of harassment is found to be highly sensitive to the disk scale-length in exponential disks, and much less so to the mass of the galaxy. In general, ram pressure stripping is found to dominate the environmental influences on infalling late-type dwarfs, while the inclusion of the harassment model produces second-order effects only. Ram pressure stripping appears capable of forming the observed cluster dwarf population, both in colour and in morphology.EThOS - Electronic Theses Online ServiceGBUnited Kingdo