Dissertation (Ph.D.)--University of Toledo, 2009. / Typescript. "Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Physics." Bibliography: leaves 113-121.

No description available.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 226-233).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

This thesis describes the results of a survey of the HI42ɑ recombination line emission at 2.3 GHz from HII regions in the Southern Milky Way, carried out with the 26 m diameter Hartebeesthoek radio telescope. The Galactic Longitude range covered was 290° to 40°. Single recombination lines were detected from 375 positions. Multiple lines were observed towards 90 positions in the inner Galaxy. No line emission could be detected in 28 positions. Continuum antenna temperatures were estimated from drift scans or radio maps observed for the purpose. LTE electron temperatures and turbulent velocities of the HII regions were calculated where possible. The properties of the sample were compared to those observed in HI09ɑ surveys. The lines observed from over 50 positions were first detections, of which half were associated with optically-identified HII regions. In about 150 cases the lines were only the second to be detected from those HII regions. The processes of the radio emission, detection, and analysis were simulated numerically. The detectability of the emission and the magnitude of non-LTE effects and pressure-broadening in multi-component HII regions was predicted and compared to observations. The radio luminosity function of the HII regions was determined over a range of three orders of magnitude in intrinsic brightness for the first time, using techniques which corrected for different types of incompleteness in the samples. The luminosity function was compared to those in five selected spiral galaxies, and shown to lie between those of M33 and M81. An alternate form of the luminosity function was developed for use with a numerical model of the spiral arm structure of the Milky Way. The physical parameters defining the major spiral arms were established by comparing synthesized diagrams of radial velocity versus Galactic Longitude with those actually observed. The faint, extended HII regions S9 and RCW129 in Scorpius, the Barnard Loop in Orion, and S296 in Canis Major were analyzed, using all available data. All the recombination lines from these HII regions were first detections

No description available.

<p>The effect of stellar feedback on the interstellar medium is investigated using numerical simulation. In particular, the roles of supernova feedback and ionization feedback on the star formation rate and structure of the interstellar medium are compared. We use Enzo, an adaptive mesh code, and employ the MUSCL-Hancock hydrodynamics scheme to run simulations of a section of a stratified galactic disk. A turbulent velocity field is imposed in the central region of the disk and self-gravity is applied. Star clusters are formed when density and temperature conditions are met, which, in turn, provide ionization and supernova feedback into the interstellar medium. Simulations were run with and without supernova and ionization feedback and the runs are compared. Ionization feedback is found to dominate over supernova feedback in regulating star formation rates. With no feedback, all the gas is converted to stars by 200 Myr. When supernova feedback is added, 98% of the gas is used to create stars by 300 Myr. With ionization feedback instead, at 1 Gyr into the run, only 30% of the gas is in stars. Even with supernova feedback added to ionization feedback, the gas converted to stars is just 29% at 1 Gyr. Very strong supernovae take this fraction down to 25%. The star formation rates in the runs with supernova feedback are consistent with the low end of the Kennicutt-Schmidt relation, while the runs without ionization feedback have star formation rates that are an order of magnitude larger. Gas phase masses and volumes produced in the ionization runs are broadly consistent with observations.</p> / Master of Science (MSc)

It has become increasingly clear that a complete picture of galaxy evolution requires a better understanding of the role of Active Galactic Nuclei (AGN). In particular, they could be responsible for regulating star formation and galaxy growth via feedback processes. There are also competing views about the main modes of stellar growth and supermassive black hole growth in galaxies that need to be resolved. With high infrared luminosities (thus star formation rates) and a frequent occurrence of AGN, galaxies selected in the far-infrared wavebands form an ideal sample to search for a connection between AGN and star formation. The first part of this thesis contains a detailed analysis of the molecular gas properties of nearby infrared luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). We find that the enhanced molecular gas density in the most IR-luminous systems can be explained by major galaxy mergers, and that AGN are more likely to reside in higher-density systems. While the frequent concurrence of AGN and galaxy mergers in ULIRGs was already established, this work provides a coherent framework that explains trends observed with five molecular gas tracers with a broad range of critical densities, and a comparison with simulations that reproduce observed molecular line ratios without invoking AGN-induced chemistry. The second part of the thesis presents an analysis of the AGN content of intermediate redshift galaxies (0.3<z<1). However, identifying complete AGN samples at these redshift is challenging because it is difficult to find X-ray weak or absorbed AGN. To alleviate this problem, we developed the Mass-Excitation (MEx) diagram, which is applicable out to redshift of 1 with existing optical spectra. It improves the overall AGN census by detecting AGN that are missed in even the most sensitive X-ray surveys. The new diagnostic was used to study the concurrence of star formation and AGN in 70 micron-selected galaxies from the Far-Infrared Deep Extragalactic Legacy survey. When multiple AGN diagnostics are combined, we find not only a high AGN fraction in FIR-selected galaxies (as high as for nearby FIR-selected galaxies), but a high incidence of X-ray absorbed AGN. These findings may have considerable implications for current views about the main mode of AGN growth.

No description available.

Optical absorption line techniques have been applied to the study of a number of translucent molecular clouds in which the total column densities are large enough that substantial molecular abundances can be maintained. Results are presented for a survey of absorption lines of interstellar C2, CH, and CN. Detections of CN through the A2II -X2E+ (1,0) and (2,0) bands of the red system are reported, and are compared with observations of the blue system for one line of sight. The population distributions in C2 provide diagnostic information on temperature and density. The measured column densities of the three species can be used to test details of the theory of molecule formation in clouds where photo -processes still play a significant role. The C2 and CH column densities are strongly correlated with each other and probably also with the H2 column density. In contrast, the CN column densities are found to vary greatly from cloud to cloud. The observations are discussed with reference to detailed theoretical models.