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Session 25 - Galaxies, Clusters of Galaxies and their Evolution.
Oral session, Monday, June 08

[25.03] Quantitative Morphology of Galaxies in the Hubble Deep Field

F. R. Marleau (UC, Berkeley), L. Simard (UCO/Lick Obs., UCSC)

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