Disentangling the Dynamical Mechanisms for Cluster Galaxy Evolution

TL;DR

This paper investigates the physical mechanisms behind the morphological transformation of galaxies in clusters, introducing a new infrared diagnostic method that suggests interaction-enhanced secular evolution as the primary cause.

Contribution

It proposes a novel infrared diagnostic approach to distinguish the mechanisms driving galaxy evolution in clusters and applies it to support interaction-enhanced secular evolution as the main process.

Findings

Infrared diagnostics can effectively differentiate galaxy transformation mechanisms.

Interaction-enhanced secular evolution is favored as the main driver of the BO effect.

The approach is demonstrated on a rich, intermediate redshift galaxy cluster.

Abstract

The determination of the dynamical causes of the morphological Butcher-Oemler (BO) effect, or the rapid transformation of a large population of late-type galaxies to earlier Hubble types in the rich cluster environment between intermediate redshifts and the local universe, has been an important unsolved problem which is central to our understanding of the general problems of galaxy formation and evolution. In this article, we survey the existing proposed mechanisms for cluster galaxy transformation, and discuss their relevance and limitations to the explanation of the morphological BO effect. A new infrared diagnostic approach is devised to disentangle the relative importance of several major physical mechanisms to account for the BO effect, and an example of the first application of this procedure to a single rich, intermediate redshift galaxy cluster is given to demonstrate the viability of this approach. The preliminary result of this analysis favors the interaction-enhanced secular evolution process as the major cause of the cluster-galaxy morphological transformation. This conclusion is also supported by a wide range of other published results which are assembled here to highlight their implications on a coherent physical origin for the morphological BO effect.