The Megamaser Cosmology Project.IX. Black hole masses for three maser
  galaxies
  As part of the Megamaser Cosmology Project (MCP), we present VLBI maps of
nuclear water masers toward five galaxies. The masers originate in sub-parsec
circumnuclear disks. For three of the galaxies, we fit Keplerian rotation
curves to estimate their supermassive black hole (SMBH) masses, and determine
(2.9 $\pm$ 0.3) $\times~10^{6}M_\odot$ for J0437+2456, (1.7 $\pm$ 0.1)
$\times~10^{7}M_\odot$ for ESO 558$-$G009, and (1.1 $\pm$ 0.2)
$\times~10^{7}M_\odot$ for NGC 5495. In the other two galaxies, Mrk 1029 and
NGC 1320, the geometry and dynamics are more complicated and preclude robust
black hole mass estimates. Including our new results, we compiled a list of 15
VLBI-confirmed disk maser galaxies with robust SMBH mass measurements. With
this sample, we confirm the empirical relation of $R_{out} \propto 0.3
M_{SMBH}$ reported in Wardle & Yusef-Zadeh (2012). We also find a tentative
correlation between maser disk outer radii and WISE luminosity. We find no
correlations of maser disk size with X-ray 2-10 keV luminosity or [O III]
luminosity.
