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We describe a method to identify inclined water maser disks orbiting massiveblack holes and to potentially use them to measure black hole masses. Due tothe geometry of maser amplification pathways, the minority of water maser disksare observable: only those viewed nearly edge-on have been identified,suggesting that an order of magnitude additional maser disks exist. We suggestthat inward-propagating masers will be gravitationally deflected by the centralblack hole, thereby scattering water maser emission out of the disk plane andenabling detection. The signature of an inclined water maser disk would benarrow masers near the systemic velocity that appear to emit from the blackhole position, as identified by the radio continuum core. To explore thispossibility, we present high resolution (0.07"-0.17") Very Large Array line andcontinuum observations of 13 galaxies with narrow water maser emission and showthat three are good inclined disk candidates (five remain ambiguous). In thebest case, for CGCG 120$-$039, we show that the maser and continuum emissionare coincident to within $3.5\pm1.4$ pc ($6.7\pm2.7$ milliarcsec). Subsequentvery long baseline interferometric maps can confirm candidate inclined disksand have the potential to show maser rings or arcs that provide a directmeasurement of black hole mass, although the mass precision will rely onknowledge of the size of the maser disk.

How to Detect Inclined Water Maser Disks (and Possibly Measure Black Hole Masses)