Author ORCID Identifier

https://orcid.org/0000-0002-5222-1337

Year of Publication

2022

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

First Advisor

Dr. Yuanyuan Su

Abstract

In the hierarchical structure formation model, galaxy clusters grow and evolve via mergers and accretion from the surrounding cosmic web, leaving distinctive marks in the gas properties, metallicity, and dynamical state at the outskirts of clusters, which needs to be probed to better understand the growth of a cluster. I probed the gas properties of four nearby galaxy groups MKW4, Antlia, RXJ1159, and ESO3060170 out to their virial radii using deep Suzaku and mostly snapshot Chandra observations. I found the gas entropy profiles of MKW4 follow a power-law at its outskirts - as expected from purely gravitational structure formation model. I measured an enclosed baryon fraction of 11% at the outskirts of MKW4, remarkably smaller than the cosmic baryon fraction of 15%, suggesting galaxy groups due to their shallow gravitation potential are vulnerable to baryon loss. I measured the average Fe abundance of four groups at their outskirts, which is remarkably uniform and strikingly similar to that of massive clusters and fully consistent with the numerical predictions from the IllustrisTNG cosmological simulation. This result support an early-enrichment scenario among galactic systems over an order of magnitude in mass even before their formation. I also studied the gas dynamics of a early-stage merging galaxy cluster, Abell 98, using deep Chandra observations. I reported the first unambiguous detection of an axial merger shock, which unveils a critical epoch in the formation of a massive galaxy cluster when two subclusters are caught in the early phase of the merging process. I also detected X-ray emission from the the warm-hot intergalactic medium (WHIM) filament, lies between two subclusters of Abell 98.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2022.358

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