paper

Galaxy morphology to I=25 mag in the Hubble Deep Field

arXiv:astro-ph/9602044 · doi:10.1093/mnras/279.3.L47

Abstract

The morphological properties of galaxies between in the {\em Hubble Deep Field} are investigated using a quantitative classification system based on measurements of the central concentration and asymmetry of galaxian light. The class distribution of objects in the {\em Hubble Deep Field} is strongly skewed towards highly asymmetric objects, relative to distributions from both the {\em HST Medium Deep Survey} at and an artificially redshifted sample of local galaxies. The steeply rising number count-magnitude relation for irregular/peculiar/merging systems at reported in Glazebrook \etal\ (1995a) continues to at least . Although these peculiar systems are predominantly blue at optical wavelengths, a significant fraction also exhibit red colours, which may indicate they are at high redshift. Beyond Glazebrook \etal 's magnitude limit the spiral counts appear to rise more steeply than high-normalization no-evolution predictions, whereas those of elliptical/S0 galaxies only slightly exceed such predictions and may turn-over beyond . These results are compared with those from previous investigations of faint galaxy morphology with HST and the possible implications are briefly discussed. The large fraction of peculiar/irregular/merging systems in the {\em Hubble Deep Field} suggests that by the conventional Hubble system no longer provides an adequate description of the morphological characteristics of a high fraction of field galaxies.

6 pages LaTeX. 4 EPS Figures. 2 Colour PS Plates. Accepted for publication in MNRAS

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