AAS 207th Meeting, 8-12 January 2006
Session 83 The COSMOS Survey
Special Session, Tuesday, 10:00-11:30am, January 10, 2006, Ballroom/Salon 2

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[83.07] Evolution of the Morphology Density Relation Between 0 < z < 1.2

P. Capak (Caltech), B. Mobasher (STScI), N. Z. Scoville (Caltech), K. Sheth (SSC), B. Abraham (University of Toronto), R. Ellis (Caltech), COSMOS Collaboration

The morphology density relation is analyzed between 0 < z < 1.2 in the COSMOS 2sq degree survey. The present COSMOS data covers densities between 1 to 200 galaxies per Mpc2 at z < 1.2. We show our surface density measurements are only affected by photometric redshift errors at the lowest densities. Hence, spectroscopic redshifts will eventually allow us to extend the density range down to 0.01 galaxies per Mpc2. We find the morphology density relation is evolving with redshift, with some evidence for stronger evolution at higher densities. The amplitude of the morphology density relation also varies with absolute magnitude. These results are qualitatively consistent with the predictions of Cold Dark Matter structure formation models.

For this study an automated galaxy morphology classifier is developed based on the Petrosian Gini parameter. The classifier is robust against band shifting and surface brightness dimming at z < 1.2. This is a significant advance over previous morphological estimators.

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