The motions of galaxies within large-scale structures

Bilton, Lawrence Edward

Abstract

Galaxy clusters represent one of the largest-scale structures in the Universe, with their en- vironments of varying density being ideal for inducing an increase in activity of the cluster galaxy members and the pervading Intracluster Medium (ICM) between them. However the precise drivers, thereby the inferred consequences, of differing states of galaxy cluster activity have not been adequately disentangled. If one can procure a sufficient dichotomic sample of cluster galaxies of differing sub-populations from relaxed and unrelaxed galaxy cluster dynamical states, one could analyse how these sub-populations ‘move’ as a function of both radius and dynamical state. Specifically, using velocity dispersion profiles (VDPs) that weight against cluster galaxies across all radii with a Gaussian window function, one can determine how cluster galaxies of properties that pertain to galaxy evolutionary indicators respond to the cluster environment as a function of the clustocentric radius. In addition, analysing the rotational profiles of these sub-populations as a function of the clustocentric radius can help identify where the bulk of the kinetic energy lies. In view of these points, we have pooled data of galaxies from the Sloan Digital Sky Survey (SDSS) two composite galaxy clusters are assembled into unrelaxed and relaxed states, which are compared with one another through splitting their cluster galaxy populations by their evol- utionary proxies (i.e. morphology, colour, mass and AGN), thus analysing their resultant VDPs and rotational profiles. It is therefore found that unrelaxed galaxy clusters possess increased interaction between cluster galaxies as the radius increases, driven by blue and red elliptical galaxies, suggesting an induction of activity by pre-processed groups. AGN- hosting cluster galaxy sub-populations within these unrelaxed environs however present increased activity as 𝑅 → 0, indicating these are recent infallers, potentially triggered due to interactions with the ICM. Rotational profiles of unrelaxed clusters build upon the VDPs, showing significant bulk rotation of cluster galaxies with prominent core rotation driven by redder sub-populations.

Citation

Bilton, L. E. The motions of galaxies within large-scale structures. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4222954

• Thesis Type: Thesis
• Deposit Date: Mar 11, 2021
• Publicly Available Date: Feb 23, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4222954
• Additional Information: Department of Physics and Mathematics, The University of Hull
• Award Date: Oct 1, 2020