Hubble space telescope imaging of the CFRS and LDSS redshift surveys III: field elliptical galaxies at 0.2 less than z less than 1.0

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Title: Hubble space telescope imaging of the CFRS and LDSS redshift surveys III: field elliptical galaxies at 0.2 less than z less than 1.0
Author(s): Schade, David J.; Lilly, Simon J.; Crampton, David; Ellis, Richard S.; Le Fevre, Olivier; Hammer, Francois; Brinchmann, Jarle; Abraham, Roberto G.; Colless, Matthew; Glazebrook, Karl; Tresse, Laurence; Broadhurst, Thomas J.
Abstract: Two-dimensional surface photometry has been performed on a magnitude-limited sample of 46 field galaxies that are classified as ellipticals based on two-dimensional fitting of their luminosity profiles using Hubble Space Telescope imaging. These galaxies are described well by a de Vaucouleurs R1/4 profile. The sample was selected from the combined Canada-France and LDSS redshift surveys and spans the redshift range 0.20 < z < 1.00. This analysis reveals several clear evolutionary trends. First, the relationship between galaxy half-light radius and luminosity evolves with redshift such that a galaxy of a given size is more luminous by ΔMB = -0.97 ± 0.14 mag at z = 0.92 relative to the local cluster elliptical relation. Second, the mean rest-frame color shifts blueward with redshift by Δ(U - V) = -0.68 ± 0.11 at z = 0.92 relative to the same relation in the Coma Cluster. These shifts in color and luminosity of field elliptical galaxies are similar to those measured for cluster ellipticals. Approximately one-third of these elliptical galaxies (independent of redshift) exhibit [O II] 3727 emission lines with equivalent widths > 15 Å, indicating ongoing star formation. Therefore, field elliptical galaxies are not composed entirely of very old stellar populations. Estimated star formation rates (SFR) together with stellar population evolutionary models imply that ≤ 5% of the stellar mass in the elliptical galaxy population has been formed since z = 1. We find some evidence that the dispersion in color among field ellipticals at z ∼ 0.55 may be larger than that seen among samples of cluster ellipticals and SO galaxies at similar redshift. We see no evidence for a decline in the space density of early-type galaxies with lookback time. Both the 〈V/Vmax〉 statistics and a comparison with local luminosity functions are consistent with the view that the population of massive early-type galaxies was largely in place by z ∼ 1. This implies that merging is not required since that time to produce the present-day space density of elliptical galaxies. However, the statistics are poor: a larger sample is required to produce a decisive result.
Publication type: Journal article
Source: Astrophysical Journal, Vol. 525, no. 1 (Nov 1999), pp. 31-46
Publication year: 1999
Keyword(s): Clusters; Color-magnitude relation; Cosmology; Disk galaxies; Elliptical; Evolution; Fundamental parameters; Fundamental plane; Galaxies; Lenticular; Luminosity function; Models; Morphological types; Observations; Photometry; Surface brightness; Surveys
Publisher: University of Chicago Press
ISSN: 0004-637X
Publisher URL: http://dx.doi.org/10.1086/307885
Peer reviewed