The Past, Present, and Groundbreaking Future of OH Megamasers

Roberts, Hayley

Graduate Thesis Or Dissertation

The Past, Present, and Groundbreaking Future of OH Megamasers Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/xp68kh70r

Abstract

OH megamasers (OHMs) are luminous masers found in (ultra-)luminous infrared galaxies ([U]LIRGs). OHMs are signposts of major gas-rich mergers associated with some of the most extreme star forming regions in our universe. In the four decades since their discovery, only 120 OHM hosts have been detected at limited redshifts despite numerous searches in an order of magnitude more galaxies. However, the dominant OH masing line, occurring at 1667 MHz, can spoof the 1420 MHz neutral hydrogen (H I) line in untargeted surveys. H I surveys on next-generation radio telescopes, such as the Square Kilometre Array (SKA) and its precursors, will detect unprecedented numbers of OHMs. This surge in detections will not only fundamentally change the landscape of the known OHM population, but will also unlock our ability to implement OHMs as tracers of major mergers and extreme star formation on cosmic scales. Here, I present predictions for the number of OHMs that will be detected by these surveys, as well as novel methods for identifying these interlopers using a k-Nearest Neighbors machine learning algorithm. Preliminary data from H I surveys on precursor SKA telescopes is used to vet and strengthen these methods, resulting in five new OHM detections of sources originally classified as H I emission. I also present two new OHM detections from SKA precursors that showcase this upcoming revolutionary science – whether it be high quality measurements of the OH masing lines or shattering the record for highest redshift OHM detection. I also reexamine the underlying conditions required to steer a major merger on the path to producing an OHM, demonstrating that our previous theories are too simplistic to describe the full population of OHMs hosts. Lastly, I present a comprehensive catalog of all known OHMs and their host galaxies, including their IR and radio properties. This catalog and the inspection of relations between OHMs and their hosts serve as a consolidated, unified resource in the era of new OHM detections.

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