Evolution of the Morphology Density Relation P. Capak, B. Mobasher, K. Sheth, R. Ellis, B. Abraham, N. Scoville.

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