Date of Award
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics and Astronomy
Committee Chair
Massimiliano Bonamente
Committee Member
Stephen Walker
Committee Member
Ming Sun
Committee Member
Richard Lieu
Committee Member
James Miller
Research Advisor
Massimiliano Bonamente
Subject(s)
Baryons, Heavy particles (Nuclear physics), Cosmology, X-rays
Abstract
A well known problem in astrophysics that has seen a significant amount of investigation in recent years is the ”missing baryons problem”, in which up to 40% of baryons have been reported missing at low redshifts [62]. Predictions show that these remaining baryons are likely residing within the Warm-Hot Intergalactic Medium (WHIM). The process of finding these baryons involves searching for absorption line systems in the WHIM, and using column densities of those absorbing ions to calculate the cosmological density of the medium. Several wide scale FUV studies (e.g. [21]) have been completed to work towards solving this problem, but there has yet to be a study of such scope in the X-ray band of wavelengths. Using a sample of 51 X-ray sources from FUSE and HST, this project seeks to be the conclusive work on the presence of WHIM absorption in X-ray quasars. Using the spectral analysis software SPEX, the sample of 51 X-ray sources was searched for O VII and O VIII absorption lines at redshifts from prior O VI and H I detections, as well as at z = 0 in search for galactic oxygen. In total, we report 8 possible absorption line systems of O VII and O VIII. Upper limits of the resultant column densities found from both the entire sample’s absorption line search and the possible detections reported were used to put ii constraints on the cosmological density of baryons in the universe due to the WHIM, ΩWHIM . These results were then compared to the baryonic density expected to be contributed by the WHIM. Being the first and only large scale X-ray search for WHIM absorption of its kind, this work gives the most comprehensive and definitive look at WHIM oxygen absorption in X-ray quasars, and an answer to the missing baryons problem.
Recommended Citation
Spence, David, "A large-sample X-ray absorption line analysis in search of the missing baryons in the hot WHIM" (2024). Dissertations. 411.
https://louis.uah.edu/uah-dissertations/411