Date of Graduation

2015

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

D J Pisano

Committee Co-Chair

Loren D Anderson

Committee Member

David T Frayer

Committee Member

Yu Gu

Committee Member

Amy M Keesee

Abstract

Luminous compact blue galaxies (LCBGs) are bright (MB ≤ --18.5), blue (B -- V ≤ 0.6), massive (M* ∼ 10 9 M[special character omitted]) star-forming galaxies with high B-band surface brightnesses (SBe(B) ≤ 21.0) that were common at z ∼ 1 when the Universe was half of its current age, but are rare in the local Universe. In this thesis, I have conducted studies of the atomic neutral hydrogen (H I) and global star formation properties of a group of the rare z ∼ 0 analogs to the common z ∼ 1 LCBGs to better understand how this class of galaxies evolves. I have first conducted a pilot study of the global star-formation properties of a heterogeneous group of local star-forming galaxies using observations at 33 GHz with the Green Bank Telescope. In this study, we made the first detections at 33 GHz for 22 of the 27 galaxies we observed. We fit spectral energy distributions (SEDs) to the galaxies¡¯ radio continuum emission from ∼ 1 GHz--40 GHz and quantified the relative contributions of thermal free-free emission from massive, short-lived stars and non-thermal synchrotron emission from supernovae. We found that these galaxies followed the radio-far-infrared correlation at 33 GHz, and that the thermal fraction at 33 GHz, spectral index from 1.4 GHz to 33 GHz, and ratio of radio continuum emission at 33 GHz to total far-infrared emission together give an estimate of the relative ages of the most recent episodes of star formation in these galaxies. In the second study, we analyzed resolved H I observations of nine z ∼ 0 LCBGs. We found that the LCBGs have a variety of H I morphologies, are rotationally-supported at all radii, and are unlikely to be forming large S0-type bulges. We also found that the disks of LCBGs are stable on average with respect to gravitational instabilities, but may have the potential to form instabilities at large radii. In addition, the LCBGs in our sample had the lowest ratios of ordered rotation to disordered motions in the centers of their disks, supporting the idea of these galaxies forming a small central bulge or bar. Finally, we applied the techniques we used in our study of the global star-formation properties of a heterogenous sample of galaxies to investigate a sample of 42 local (D < 80 Mpc) LCBGs. We found that LCBGs all have evidence of ongoing star formation, though the ages of their most recent episodes of star formation are varied. We also saw that LCBGs without star-forming clumps appeared to have relatively young star formation ages (∼ 30 Myr), while clumpy LCBGs could have a range of ages, from very young to ∼ 100 Myr or more. We conclude that there are likely to be at least two broad causes of star formation in LCBGs, and that their evolutionary paths are likely to be diverse.

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