Author ORCID Identifier
Date Available
1-24-2024
Year of Publication
2024
Degree Name
Doctor of Philosophy (PhD)
Document Type
Doctoral Dissertation
College
Arts and Sciences
Department/School/Program
Physics and Astronomy
First Advisor
Dr. Gary J. Ferland
Second Advisor
Dr. Marios Chatzikos
Abstract
Over 90% of baryonic matter in the universe exists as astrophysical plasmas. The gas
is often far from thermodynamic equilibrium, so numerical non-equilibrium spectral
synthesis simulations are used to understand observations. cloudy simulates vari-
ous physical conditions, providing spectra predictions. This thesis aims to meet the
challenge of new observatories like the JWST (James Webb Space Telescope) and
XRISM (X-Ray Imaging Spectroscopy Mission). These simulations are no better
than the underlying atomic and molecular database and the fourth chapter details
a long-needed update to an evolving database. The predicted spectra are strongly
affected by the composition of the gas, which is determined in part by the condensa-
tion of certain elements into solid particles called “dust grains”. I showed the effects
of self-consistently depleting abundances within H ii regions, using the Orion Nebula
to demonstrate changes to the spectrum as the degree of dust depletion is altered.
Next, an analysis of emergent strong spectral-line intensities is obtained by calcu-
lating the abundances into cloudy models of a family of extragalactic H ii regions.
These predictions are then compared with Sloan observations to constrain the de-
pletion strength for a large sample of extragalactic H ii regions. These two projects
impact the interpretation of JWST observations. Finally, I improved the treatment
of one-electron doublets, allowing us to simulate observations from the new genera-
tion of X-ray microcalorimeters. These advances impact projects using NASA’s most
recent orbital observatories, JWST and XRISM.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2024.129
Recommended Citation
Gunasekera, Chamani, "Exploring the Hot and Gaseous Universe from Infrared to X-ray" (2024). Theses and Dissertations--Physics and Astronomy. 122.
https://uknowledge.uky.edu/physastron_etds/122
