Are Boxy/Disky Ellipticals Dependent on Environment?

Abstract

Boxy and disky isophotes in elliptical galaxies are an imprint of their formation history. It is thus interesting to examine the boxyness of early-type galaxies as a function of environment in large cluster systems, especially as some N-body simulations also predict a higher number of disky versus boxy ellipticals in overdense regions. Using high-resolution HST data from the Stages survey, centred on the Abell901/902 supercluster at a redshift of z ∼ 0. 167, we investigate this dependence. Taking extreme care of the setup of the codes used (particularly ellipse), we analyse a sample of ∼ 560 ellipticals and S0 galaxies, one of the biggest samples examined for this effect. Although other groups have found environmental dependencies before, no such dependence is found in the Stages survey data. The ratio of boxy to disky galaxies stays constant over the entire range of environment and galaxy density present in the field examined.