Dissertation/Thesis Abstract

X-ray and FUV observations of starburst galaxies: Probing galactic feedback at high energies
by Grimes, John P., Ph.D., The Johns Hopkins University, 2008, 292; 3295795
Abstract (Summary)

Galactic scale outflows powered by star formation are thought to play an important cosmological role in galaxy evolution and formation. These “superwinds” drive enriched gas, dust, and energy out of host galaxies into the intergalactic medium. They could enrich the next generation of galaxies, suppress low mass galaxy formation, quench star formation within the host galaxy, and allow ultraviolet (UV) ionizing photons from high mass stars to escape the galaxy and reionize the universe. Therefore, understanding galactic scale outflows is an important next step in cosmological research. Studies of these outflows at high redshifts are constrained by observational limits, especially at high energies. Therefore, in this work we have compiled and analyzed the largest samples to date of high quality X-ray and far-ultraviolet (FUV) observations of star-forming galaxies.

Our X-ray observations show the universal presence of hot, metal enriched gas around these star-forming galaxies with properties that scale with the physical parameters of the host galaxies. This is consistent with the hot gas being produced in shocks driven by a galactic “superwind” powered by the kinetic energy collectively supplied by stellar winds and supernovae. In the FUV sample, our observations suggest the almost ubiquitous presence of galactic outflows. We find that outflow velocity increases with line strength, suggesting that the stronger lines probe lower column density gas entrained in the outflows than the weaker absorption features. O VI emission is not generally observed in our sample, showing that coronal gas cooling is not significant in slowing the expansion of galactic outflows Lastly, we find no evidence of Lyman continuum emission escaping from any of the galaxies in this work. Taken together, our analysis provides a more complete physical basis for understanding the outflows that seem to be a ubiquitous features of LBGs. This insight is vital for understanding the role that such outflows play in the evolution of galaxies and the intergalactic medium. Our work provides a unique window on global properties of local star-forming galaxies as observed in the FUV and X-ray and is a useful comparison sample for understanding the properties of high redshift LBGs.

Indexing (document details)
Advisor: Heckman, T.
Commitee:
School: The Johns Hopkins University
School Location: United States -- Maryland
Source: DAI-B 69/01, Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Astronomy
Keywords: Far-ultraviolet observations, Galactic feedback, Starburst galaxies, Starbursts
Publication Number: 3295795
ISBN: 9780549404880
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