  The co-evolution of galaxies and supermassive black holes (SMBHs) underpins
our understanding of galaxy evolution, but different methods to measure SMBH
masses have only infrequently been cross-checked. We attempt to identify
targets to cross-check two of the most accurate methods, megamaser and cold
molecular gas dynamics. Three promising galaxies are selected from all those
with existing megamaser SMBH mass measurements. We present Atacama Large
Millimeter/sub-millimeter Array (ALMA) 12CO(2-1) and 230-GHz continuum
observations with angular resolutions of about 0.5". Every galaxy has an
extended rotating molecular gas disc and 230-GHz continuum source(s), but all
also have irregularities and/or non-axisymmetric features: NGC1194 is highly
inclined and has disturbed and lopsided central 12CO(2-1) emission; NGC3393 has
a nuclear disc with fairly regular but patchy 12CO(2-1) emission with little
gas near the kinematic major axis, faint emission in the very centre and two
brighter structures reminiscent of a nuclear ring and/or spiral; NGC5765B has a
strong bar and very bright 12CO(2-1) emission concentrated along two
bisymmetric offset dust lanes and two bisymmetric nuclear spiral arms.
12CO(2-1) and 12CO(3-2) observations with the James Clerk Maxwell Telescope are
compared with the ALMA observations. Because of the disturbed gas kinematics
and the impractically long integration times required for higher angular
resolution observations, none of the three galaxies is suitable for a future
SMBH mass measurement. Nonetheless, increasing the number of molecular gas
observations of megamaser galaxies is valuable, and the ubiquitous disturbances
suggest a link between large-scale gas properties and the existence of
megamasers.
