Evolution of the Morphology Density Relation

P. Capak, B. Mobasher, K. Sheth, R. Ellis, B. Abraham, N. Scoville

Morphology Density

• Increase in the fraction of early type galaxies with increased density– Environmental effect

• Morphology Classifier

• Density measure

• Evolution of the relation

Morphology Classifier

• Classified 1000 galaxies by eye in F814W and/or F606W bands

• Cleanest division based on Gini and Asymmetry

• Must be careful of redshift dependent effects

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

• Reproduce the morphology density relation at middle densities at all redshifts

Morphology Density Relation

Redshift Evolution

• Rate of Elliptical formation is higher in high density regions

• However Ellipticals still form in the field

Cosmic Time (yr)

Elliptical formation rate