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J. Darling (Cornell University)
This thesis presents a survey for OH megamasers conducted at the Arecibo observatory covering one quarter of the sky to a depth of one gigaparsec. The survey doubles the number of known OH megamasers, derives the first flux-limited OH luminosity function, and quantifies the relationship between luminous infrared galaxies and OH megamasers. The survey builds the foundation required to employ OH megamasers as tracers of major galaxy mergers, dust-obscured star formation, and the formation of supermassive black hole binaries spanning the epoch of galaxy evolution to the present. The OH luminosity function predicts the sky density and detectability of OH megamasers in deep radio surveys and indicates that OH megamasers become the dominant radio emission line beyond z=0.3. OH megamasers may have a high sky density such that any sufficiently deep observation (below 0.1 mJy RMS noise) will reveal up to dozens of OH megamasers per square degree per 50 MHz around z=1-2.
Supporting optical photometry, spectroscopy, and radio observations are combined with an extensive literature and database survey to explore the relationships between active galactic nuclei and OH megamasers and to identify the environments which favor OH megamaser production. Significant trends are few, but there is a strong indication that OH megamasers are produced only in advanced mergers during a short time interval spanning perhaps 108 years. There are also indications that OH megamaser hosts tend to be warmer and more luminous than the merger population overall. Relationships between host properties and OH spectral line properties are poor, including the OH-FIR relationship. The OH-FIR relationship indicates (with much scatter) that OH megamasers are mostly saturated.
This dissertation was supported by NSF grant AST 00-98526 and STScI grant AR-08373.01-97A.
The author(s) of this abstract have provided an email address for comments about the abstract: darling@astro.cornell.edu