When do early-type galaxies form?
/ Authors
Roberto Abraham, Patrick J. McCarthy, E. Mentuch, K. Glazebrook, P. Nair, Jean-Ren'e Gauthier, S. Savaglio, D. Crampton, S. Juneau, R. Murowinski
and 21 more authors
D. L. Borgne, R. Carlberg, I. Jørgensen, K. Roth, Hsiao-Wen Chen, Ronald O. Marzke Department of AstronomyAstrophysics, U. Toronto, Observatories of the Carnegie Institution of Washington, Centre for Gravitational Astrophysics, Supercomputing, S. U. O. Technology, Max-Planck-Institut fur extraterrestrische Physik, H. I. O. Astrophysics, S. Observatory, U. Arizona, G. Observatory, Dept. of AstronomyAstrophysics, U. Chicago, D. Physics, Astronomy, San Francisco State University
/ Abstract
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.
Journal: Proceedings of the International Astronomical Union