1996/07/31 by Richard S. Ellis, Ian Smail, Alan Dressler +8 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/304261
published as Astrophys.J.483:582,1997 · 27 pages, LaTeX, 15 figures, including 3 plates (jpg format). Revised text, ApJ in press. Postscript figures 1a-c also available at http://star-www.dur.ac.uk/~irs/duv.figs.tar.gz
arxiv created 1997/02/05 · openalex publication_date 1997/07/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The small scatter observed for the ( U - V ) colors of spheroidal galaxies in nearby clusters of galaxies provides a powerful constraint on the history of star formation in dense environments. However, with local data alone, it is not possible to separate models where galaxies assembled synchronously over redshifts 0 < z < 1 from ones where galaxies formed stochastically at much earlier times. Here we attempt to resolve this ambiguity via high-precision rest-frame UV-optical photometry of a large sample of morphologically selected spheroidal galaxies in three z ~ 0.54 clusters that have been observed with the Hubble Space T elescope ( HST ). We demonstrate the robustness of using the HST to conduct the morphological separation of spheroidal and disk galaxies at this redshift and use our new data to repeat the analysis conducted locally at a significant look-back time. We find a small scatter (<0.1 mag rms) for galaxies classed as E's and E/S0's, both internally within each of the three clusters and externally from cluster to cluster. We do not find any trend for the scatter to increase with decreasing luminosity down to L ~ L * V +3, other than can be accounted for by observational error. Neither is there evidence for a distinction between the scatter observed for galaxies classified as ellipticals and S0. Our result provides a new constraint on the star formation history of cluster spheroidals prior to z ≃ 0.5 confirming and considerably strengthening the earlier conclusions. Most of the star formation in the elliptical galaxies in dense clusters was completed before z ≃ 3 in conventional cosmologies. Although we cannot rule out the continued production of some ellipticals, our results do indicate an era of initial star formation consistent with the population of star-forming galaxies recently detected beyond z ≃ 3.