Physical Sciences and Mathematics Commons^™

The Structure Of Broad Line Region And The Effects Of Cooling Function In Active Galactic Nuclei, Ye Wang

Theses and Dissertations--Physics and Astronomy

Active Galactic Nuclei (AGNs) are the most mystic objects in the universe. They are usually very far away from our Galaxy, which means that they are ancient objects. They are also luminous and have unique features in their spectra. Studying AGNs helps understanding the early universe and the evolution of galaxies. This Dissertation aims to research the structure of AGNs and the cooling function in the AGNs environment.

I first investigate what optical/ultraviolet spectroscopic features would be produced by Broad-line Region (BLR) clouds crossing our line of sight to the accretion disk, the source of the optical/UV continuum. This research, …

Modeling Ionized And Molecular Regions Of The Interstellar Medium Using The Spectral Synthesis Code Cloudy, Gururaj Wagle

Theses and Dissertations--Physics and Astronomy

The focus of this dissertation is to study the star-forming regions of the interstellar medium (ISM), using two very diverse environments: the Polaris Flare, high-galactic latitude, cirrus cloud complex consisting of several starless molecular cores with no nearby hot stars; and the Orion Nebula, which is the closest massive star forming region. The two environments provide a wide range of physical conditions.

It is commonly assumed that the Herschel far-infrared (FIR) fluxes are a good measure of column density, hence, mass of interstellar clouds. We find that the FIR fluxes are insensitive to the column density if A_V ≳ …

A New Set Of Spectroscopic Metallicity Calibrations For Rr Lyrae Variable Stars, Eckhart Spalding

Theses and Dissertations--Physics and Astronomy

RR Lyrae stars are old, iron-poor, Helium-burning variable stars. RR Lyraes are extremely useful for tracing phase-space structures and metallicities within the galaxy because they are easy to identify, have consistent luminosities, and are found in large numbers in the galactic disk, bulge, and halo. Here we present a new set of spectroscopic metallicity calibrations that use the equivalent widths of the Ca II K, Hγ, and Hδ lines to calculate metallicity values. Applied to spectroscopic survey data, these calibrations will help shed light on the evolution of the Milky Way and other galaxies.

Reevaluation Of The Aapm Tg-43 Brachytherapy Dosimetry Parameters For An 125I Seed, And The Influence Of Eye Plaque Design On Dose Distributions And Dose-Volume Histograms, Prakash Aryal

Theses and Dissertations--Physics and Astronomy

The TG-43 dosimetry parameters of the Advantage^{TM 125}I model IAI-125A brachytherapy seed were studied. An investigation using modern MCNP radiation transport code with updated cross-section libraries was performed. Twelve different simulation conditions were studied for a single seed by varying the coating thickness, mass density, photon energy spectrum and cross-section library. The dose rate was found to be 6.3% lower at 1 cm in comparison to published results. New TG-43 dosimetry parameters are proposed.

The dose distribution for a brachytherapy eye plaque, model EP917, was investigated, including the effects of collimation from high-Z slots. Dose distributions for …