The Rotational Profiles of Cluster Galaxies

TL;DR

This study investigates the rotational profiles of galaxy clusters using observational data and hydrodynamic simulations to understand their dynamical histories and the effects of mergers and core interactions.

Contribution

It combines observational analysis of galaxy clusters with FLASH hydrodynamic simulations to explore how mergers influence rotational profiles and core dynamics.

Findings

Merging clusters show stronger core rotation within 0.5 r200.

Blue galaxy sub-populations exhibit high rotational velocities until mixing occurs.

Dumbbell cluster core rotations are influenced by galaxy motions during relaxation.

Abstract

We compile two samples of cluster galaxies with complimentary hydrodynamic and N-body analysis using FLASH code to ascertain how their differing populations drive their rotational profiles and to better understand their dynamical histories. We select our main cluster sample from the X-ray Galaxy Clusters Database (BAX), which are populated with Sloan Digital Sky Survey (SDSS) galaxies. The BAX clusters are tested for the presence of sub-structures, acting as proxies for core mergers, culminating in sub-samples of 8 merging and 25 non-merging galaxy clusters. An additional sample of 12 galaxy clusters with known dumbbell components is procured using galaxy data from the NASA/IPAC Extragalactic Database (NED) to compare against more extreme environments. BAX clusters of each sample are stacked onto a common RA-DEC space to produce rotational profiles within the range of $0.0 - 2.5$ $r_{200}$. Merging stacks possess stronger core rotation at $\lesssim 0.5 r_{200}$ primarily contributed by a red galaxy sub-population from relaxing core mergers, this is alongside high rotational velocities from blue galaxy sub-populations, until, they mix and homogenise with the red sub-populations at $\sim r_{200}$, indicative of an infalling blue galaxy sub-population with interactive mixing between both sub-populations at $\gtrsim r_{200}$. FLASH code is utilised to simulate the merger phase between two originally independent clusters and test the evolution of their rotational profiles. Comparisons with the dumbbell clusters leads to the inference that the peculiar core rotations of some dumbbell clusters are the result of the linear motions of core galaxies relaxing onto the potential during post second infall.