1. 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

2. 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

3. 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

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

5. 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

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

9. 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

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

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

12. 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

13. 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