Turning Trash into Treasure: How OH megamasers are contaminating next-generation HI surveys and what they can tell us about galaxy evolution

OH megamasers (OHMs) are rare, luminous masers found in (ultra-)luminous infrared galaxies ([U]LIRGs). The dominant OH masing line at 1667 MHz can spoof the 1420 MHz neutral hydrogen (HI) line in untargeted HI emission line surveys. This ambiguity creates a potential source of “contamination” in HI surveys, particularly for next-generation surveys that will reach groundbreaking sensitivities and redshifts. In this talk, I will present predictions for the number of OHMs that will be detected by these surveys and novel methods for identifying these interlopers using a k-Nearest Neighbors machine learning algorithm. Preliminary data from next-generation HI surveys on precursor Square Kilometre Array (SKA) telescopes is being used to vet and strengthen these methods as well as give us a first look at a new era in OHM science. From a detection of one of the most luminous OHMs to a discovery with a record-shattering redshift, these new sources are glimpses into how our understanding of the known OHM population will soon be expanding and shifting rapidly and how they will influence our understanding of galaxy evolution. Further, I will also present a fresh look at the underlying physical conditions found in OHMs. 

20/04/2022 - 12:30
Dr. Hayley Roberts
University of Colorado, Boulder, Colorado, USA.