When do early-type galaxies form?
Abstract
We have used the Hubble Space Telescope's Advanced Camera for Surveys to measure the mass density function of morphologically selected early-type galaxies in the Gemini Deep Deep Survey fields, over the redshift range 0.9 < z < 1.6. Our imaging data set covers four well-separated sight-lines, and is roughly intermediate (in terms of both depth and area) between the GOODS/GEMS imaging data, and the images obtained in the Hubble Deep Field campaigns. Our images contain 144 galaxies with ultra-deep spectroscopy, and they have been analyzed using a new purpose-written morphological analysis code which improves the reliability of morphological classifications by adopting a 'quasi-petrosian' image thresholding technique. We find that at z = 1 approximately 70% of the stars in massive galaxies reside in early-type systems. This fraction is remarkably similar to that seen in the local Universe. However, we detect very rapid evolution in this fraction over the range 1.0 < z < 1.6, suggesting that in this epoch the strong color-morphology relationship seen in the nearby Universe is beginning to fall into place.
Keywords
Cite
@article{arxiv.astro-ph/0611322,
title = {When do early-type galaxies form?},
author = {Roberto G. Abraham and Patrick J. McCarthy and Erin Mentuch and Karl Glazebrook and Preethi Nair and Jean-Rene Gauthier and Sandra Savaglio and David Crampton and Stephanie Juneau and Richard Murowinski and Damien Le Borgne and R. G. Carlberg and Inger Jorgensen and Kathy Roth and Hsiao-Wen Chen and Ronald O. Marzke},
journal= {arXiv preprint arXiv:astro-ph/0611322},
year = {2009}
}
Comments
4 pages, 2 figures, Invited talk at IAU Symposium 235, Prague, August 2006