Masers in AGN environments

Galactic nuclei are well known sources of OH and H₂O maser emission. It appears that intense star formation in ultra-luminous infrared galaxies drives most OH sources. In contrast, nuclear activity appears to drive most H₂O sources. When H₂O emission originates in accretion disk structures, constrained geometry and dynamics enable robust interpretation of spectroscopic and imaging data. The principal science includes study of AGN geometry at parsec and sub-parsec radii and measurement of geometric distances in the Hubble Flow. New high accuracy estimates of the "Hubble constant, H○" obtained from maser distances may enable new substantively improved constraints on fundamental cosmological parameters (e.g., dark energy).