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Session 25 - Galaxies, Clusters of Galaxies and their Evolution.
Oral session, Monday, June 08
We measure quantitative structural parameters of galaxies in the Hubble Deep Field (HDF) on the drizzled F814W images. Our structural parameters are based on a two-component surface brightness made up of a Sérsic profile and an exponential profile. We compare our results to the visual classification of van den Bergh et al. (1996) and the C-A classification of Abraham et al. (1996). Our morphological analysis of the galaxies in the HDF indicates that the spheroidal galaxies, defined here as galaxies with a dominant bulge profile, make up for only a small fraction, namely 8% of the galaxy population down to m_F814W(AB) = 26.0. We show that the large fraction of early-type systems in the van den Bergh sample is due to the misclassification of small round galaxies with half-light radii < 0.31 arcsec. We find that the majority of distant galaxies (z>2) in our sample with spectroscopic redshifts are disk-dominated. We also discuss the properties of a subset of HDF galaxies which have profiles flatter than a pure exponential profile.
Program listing for Monday