The morphology of faint galaxies in medium deep survey images using WFPC2

R. E. Griffiths, S. Casertano, K. U. Ratnatunga, L. W. Neuschaefer, R. S. Ellis, G. F. Gilmore, K. Glazebrook, B. Santiago, J. P. Huchra, Rogier Windhorst, S. M. Pascarelle, R. F. Green, G. D. Illingworth, D. C. Koo, A. J. Tyson

Research output: Contribution to journalArticle

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Abstract

First results from HST Medium Deep Survey images taken with WFPC2 demonstrate that galaxy classifications can be reliably performed to magnitudes I814 ≲ 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of z̄ ∼ 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, 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. However, the most intriguing result is the relatively high proportion (∼40%) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the "faint blue galaxy" problem.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume435
Issue number1 PART 2
StatePublished - Nov 1 1994

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galaxies
proportion
compact galaxies
angular resolution
brightness
stars

Keywords

  • Cosmology: observations
  • Galaxies: evolution
  • Galaxies: general
  • Galaxies: peculiar
  • Galaxies: structure
  • Surveys

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Griffiths, R. E., Casertano, S., Ratnatunga, K. U., Neuschaefer, L. W., Ellis, R. S., Gilmore, G. F., ... Tyson, A. J. (1994). The morphology of faint galaxies in medium deep survey images using WFPC2. Astrophysical Journal, 435(1 PART 2).

The morphology of faint galaxies in medium deep survey images using WFPC2. / Griffiths, R. E.; Casertano, S.; Ratnatunga, K. U.; Neuschaefer, L. W.; Ellis, R. S.; Gilmore, G. F.; Glazebrook, K.; Santiago, B.; Huchra, J. P.; Windhorst, Rogier; Pascarelle, S. M.; Green, R. F.; Illingworth, G. D.; Koo, D. C.; Tyson, A. J.

In: Astrophysical Journal, Vol. 435, No. 1 PART 2, 01.11.1994.

Research output: Contribution to journalArticle

Griffiths, RE, Casertano, S, Ratnatunga, KU, Neuschaefer, LW, Ellis, RS, Gilmore, GF, Glazebrook, K, Santiago, B, Huchra, JP, Windhorst, R, Pascarelle, SM, Green, RF, Illingworth, GD, Koo, DC & Tyson, AJ 1994, 'The morphology of faint galaxies in medium deep survey images using WFPC2', Astrophysical Journal, vol. 435, no. 1 PART 2.
Griffiths RE, Casertano S, Ratnatunga KU, Neuschaefer LW, Ellis RS, Gilmore GF et al. The morphology of faint galaxies in medium deep survey images using WFPC2. Astrophysical Journal. 1994 Nov 1;435(1 PART 2).
Griffiths, R. E. ; Casertano, S. ; Ratnatunga, K. U. ; Neuschaefer, L. W. ; Ellis, R. S. ; Gilmore, G. F. ; Glazebrook, K. ; Santiago, B. ; Huchra, J. P. ; Windhorst, Rogier ; Pascarelle, S. M. ; Green, R. F. ; Illingworth, G. D. ; Koo, D. C. ; Tyson, A. J. / The morphology of faint galaxies in medium deep survey images using WFPC2. In: Astrophysical Journal. 1994 ; Vol. 435, No. 1 PART 2.
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abstract = "First results from HST Medium Deep Survey images taken with WFPC2 demonstrate that galaxy classifications can be reliably performed to magnitudes I814 ≲ 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of z̄ ∼ 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, 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. However, the most intriguing result is the relatively high proportion (∼40{\%}) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the {"}faint blue galaxy{"} problem.",
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