The physical parameters of the evolving population of faint galaxies

Abstract

The excess numbers of blue galaxies at faint magnitudes is a subject of much controversy. Recent Hubble Space Telescope results has 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: Firstly that the population of objects classified as `peculiar' are intrinsically luminous in the optical ($M_B\sim -19$). Secondly these systems tend to be strong sources of [OII] 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 ($z>0.3$).

17 pages. 6 figures (embedded), MNRAS in press

Cited by in corpus (15)

• A New Approach to Galaxy Morphology: I. Analysis of the Sloan Digital Sky Survey Early Data Release
• The Galaxy Luminosity Function at z < 0.05: Dependence on Morphology
• Cluster vs. Field Elliptical Galaxies and Clues on their Formation
• Dynamics of blue compact galaxies, as revealed by their H$\alpha$ velocity fields II. Mass models and the starburst triggering mechanism
• Astrophysical and Astrobiological Implications of Gamma-Ray Burst Properties
• Decaying Cold Dark Matter Model and Small-Scale Power
• Optical-Infrared Colour Distribution of a Statistically-Complete Sample of Faint Field Spheroidal Galaxies
• Double Starbursts Triggered by Mergers in Hierarchical Clustering Scenarios
• On the global structure of distant galactic disks
• The Evolution of the Galaxy Sizes in the NTT Deep Field: a Comparison with CDM Models
• The Hubble Space Telescope WFPC2 B-Band Parallel Survey: A Study of Galaxy Morphology for 18 < B < 27 mag
• Modelling ISO Galaxy Counts with Luminosity and Merger Rate Evolution
• Segregated Optical-NIR colour distributions of MDS galaxies
• A Color Analysis of the NICMOS Parallel Image Archive
• On the Determination of Star Formation Rates in Evolving Galaxy Populations