Morphological Evolution of Galaxies

Abstract

The morphological evolution of galaxies as a function of redshift is studied using two quantitative structural parameters R_n (galaxy radius) and X (high spatial frequency power). A direct comparison is made between nearby and distant (0.2 < z < 1) galaxies in the Hubble Deep Field (HDF) by following the 4500 Å rest-frame wavelength range. Few if any of the HDF galaxies are similar in size and in star formation rate to dwarf galaxies such as NGC 4449 and NGC 1569. The majority of HDF galaxies have sizes comparable to local giant galaxies and are slightly more lumpy than normal galaxies. Dwarf galaxies undergoing high rates of star formation are unlikely to be local counterparts of the high-redshift population of galaxies. Based exclusively on the structural parameters studied here, giant galaxies undergoing intensive rates of star formation (giant star-burst galaxies) are possible local counterparts of the high-redshift irregular galaxies.