The physical parameters of the evolving population of faint galaxies |
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| Authors: | Karl Glazebrook Roberto Abraham Basilio Santiago Richard Ellis & Richard Griffiths |
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| Institution: | Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia,;Institute of Astronomy, Madingley Road, Cambridge CB3 0HA,;Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore MD21218, USA |
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| Abstract: | The excess number of blue galaxies at faint magnitudes is a subject of much controversy. Recent Hubble Space Telescope results have revealed a plethora of galaxies with peculiar morphologies tentatively identified as the evolving population. We report the results of optical spectroscopy and near-infrared photometry of a sample of faint HST galaxies from the Medium Deep Survey to ascertain the physical properties of the faint morphological populations. We find four principal results. First, the population of objects classified as 'peculiar' are intrinsically luminous in the optical ( M B ∼ −19). Secondly these systems tend to be strong sources of O II ] line luminosity. Thirdly the optical–infrared colours of the faint population (a) confirm the presence of a population of compact blue galaxies and (b) show the stellar populations of irregular/peculiar galaxies encompass a wide range in age. Finally a surface-brightness comparison with the local galaxy sample of Frei et al. shows that these objects are not of anomalously low surface brightness, rather we find that all morphological classes have evolved to a higher surface brightness at higher redshifts ( z > 0.3). |
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| Keywords: | surveys galaxies: evolution galaxies: peculiar galaxies: structure cosmology: observations |
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