The Effect of Dense Cluster Environments on Galactic Properties

Abstract

Abstract Galaxy clusters are extremely over dense regions of the universe and are therefore ideal for testing how galaxy properties vary with environment. We analyze a sample of >3000 galaxy spectra from 100 galaxy cluster fields, and examine trends in redshift, Dn4000, and a formulated in-fall proxy for member and non-member galaxies. The 4000 Å break (Dn4000) reveals information about the age of each galaxy, and the product of the normalized peculiar velocity and the normalized projected radius of each cluster galaxy serves as a proxy for in-fall time, or how recently each galaxy became gravitationally bound to its cluster. We see a relationship between Dn4000 and the in-fall proxy, with more recently in-fallen galaxies being systematically younger; we interpret this trend as the effect of environmental quenching of cluster galaxies. Furthermore, we see a trend in which all cluster galaxies become older with decreasing redshift, independent of in-fall proxy.