Prop. Type: GTO/NICMOS
Sci Categ: G&C (Galaxies and Clusters)
Title: Galaxy Evolution in Rich Clusters
PI: J. M. HILL (University of Arizona)
We propose to use HST and NICMOS to study the morphological and spectral evolution of galaxies within the cluster environment. By obtaining high-resolution images of galaxies in clusters at redshifts between 0.06 and 0.9, we plan to study the evolution of galaxies from lookback times approaching their formation until the present. Concurrent study of cluster properties and the local environment of the galaxies will indicate the effects of the cluster environment on galaxy evolution. Of particular interest is the morphology of galaxies at near-infrared wavelengths in clusters which show an excess of blue galaxies (Butcher-Oemler effect). We also will study the evolution of dominant central cluster galaxies and how these galaxies are affected by x-ray gas cooling flows. In A1795 we are imaging the region of the central galaxy at the wavelength of redshifted Paschen-alpha to study the emission in the region of the dust lanes discovered by WFPC. The rich clusters also act as gravitational lenses of background galaxies at higher redshift. We will use the lensed images to map the cluster gravitational potential and to study the infrared morphology of the distant source galaxies. Typical exposure times in filter F160W are set to reach a surface brightness level of H = 22.5 mag per square arcsec with a S/N of 10 per pixel. Coordinated parallel images will be used to study galaxies in the outer regions of each cluster.
Keywords: galaxy clusters, galaxies, gravitational lens
Target List: CL0939+47, Abell 1795, CL0024+16, CL1603+4313