Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/43373

Title

The HST Medium Deep Survey: galaxy morphology at high redshift

Author(s)

Griffiths, R.;  Ratnatunga, K. U.;  Casertano, S.;  Im, M.;  Neuschaefer, L. W.;  Ellis, R.;  Gilmore, G.;  Elson, R. A. W.;  Glazebrook, Karl;  Santiago, B.;  Windhorst, R. A.;  Driver, Simon P.;  Ostrander, E. J.;  Mutz, S. B.;  Koo, D. C.;  Illingworth, G. D.;  Forbes, Duncan A.;  Phillips, A. C.;  Green, R. F.;  Huchra, J. P.;  Tyson, A. J.

Abstract

With HST and WFPC2, galaxies in the Medium Deep Survey can be reliably classified to magnitudes I-814 less than or similar to 22.0 in the F814W band, at a mean redshift (z) over bar similar to 0.5. The main result is the relatively high proportion (similar to 40%) of objects which are in some way irregular or anomalous, and which are of relevance in understanding the origin of the familiar excess population of faint galaxies. These diverse objects include compact galaxies, apparently interacting pairs, galaxies with superluminous starforming regions and diffuse low surface brightness galaxies of various forms. The 'irregulars' and 'peculiar' galaxies contribute most of the excess counts in the I-hand at our limiting magnitude, and may explain the 'faint blue galaxy' problem. At least half of the faint galaxies, however, appear to be similar to regular Hubble-sequence examples observed at low redshift. Furthermore, the relative proportion of spheroidal and disk systems of normal appearance is as expected from nearby samples, indicating that the bulk of the local galaxy population was in place at half the Hubble time. Little or no evolution in the properties of these galaxies has been observed.

Publication type

Conference paper

Source

Proceedings of the 168th Symposium of the International Astronomical Union 'Examining the Big Bang and Diffuse Background Radiations', The Hague, Netherlands, 23-26 August 1994 / Menas Kafatos, Yoji Kondo (eds.), pp. 219-227

Publication year

1996

Keyword(s)

Evolution;  High redshift;  HST;  Medium Deep Survey;  WFPC2

Publisher

Kluwer Academic Publishers

ISSN

0074-1809 (series ISSN)

ISBN

0792338146

Publisher URL

http://www.iau.org/science/publications/

Copyright

Copyright © 1996 IAU.

Peer reviewed