Redshift Evolution Of The Morphology Density Relation Peter Capak B. Mobasher, R. Abraham, R. Ellise, K. Sheth, N. Scoville Postdoctoral Fellow California Institute of Technology Thank everyone Talk about backgrounds, each one different, each one

Morphology Density P. Capak,B. Mobasher, R. Abraham, R. Ellise, K Morphology Density P. Capak,B. Mobasher, R. Abraham, R. Ellise, K. Sheth, N. Scoville Higher Spheroid (E + S0) galaxies in high density regions (Dressler et. Al. 1980) Seen up to z~1 (Dressler et. Al. 1996, Smith et. Al. 2004, Postman et. Al. 2005) Possible differential evolution with redshift (Smith et. al. 2004) Systematic Effects Morphological classification Density measurement

Morphological Classification Eyeball classification is the traditional method Not practical for ~500,000 galaxies Need automated classifier Not free from systematic effects COSMOS is only one band (F814W) Classifier must be independent of band shifting Surface brightness dimming a problem Classifier must be independent of surface brightness

Same from ground and HST Pick out much more structure in HST color

Petrosian Parameter Petrosian raidus free of surface brightness dimming effects Eye and isophotal parameters are sensitive to these Defined at first minima in enclosed flux divided by radius Gini takes overall light distribution into account Cleanly divides E+S0 population from spirals and Irregular galaxies

Morphological Classification Chose to use Gini and Asymetry Gini is similar to concentration but considers total light distribution Similar to Abraham et. Al. 1996 and CAS system used by GEMS

Density Estimator Used a version of Dressler’s projected density Area defined by 10th nearest neighbor a with Mv<-21 Count out from center until there are statistically 10 objects at the same redshift as the object of interest Density error is constant with density Works well at high density, fails at “critical” low density Lowest density determined by redshift accuracy

Morphology and SED Type Elliptical and SED type are correlated However not directly Especially Irregular Galaxies

Morphology Density Relation Reproduce the morphology density relation at middle densities at all redshifts Smith et. Al. working below the “Critical” density

Differential Evolution? Stronger evolution at higher density? Highest density points from different surveys Lowest density points biased to lower evolution by density measure Waiting for more data and Spectroscopic redshifts

Conclusions Elliptical and spiral galaxies can be separated with single band morphologies Density can be measured with photometric redshift accuracy Morphology Density relation is differentially evolving However No “Critical” density