Radio properties of H2O maser host galaxies
  The 6 cm and 20 cm radio continuum properties of all 85 galaxies with
reported 22 GHz H2O maser emission and luminosity distance D > 0.5 Mpc are
studied. For the total of 55 targets for which both 6 cm and 20 cm measurements
exist and for the subsample of 42 sources with masers related to active
galactic nuclei (AGN), a spectral index could be determined from an assumed
power-law dependence. The mean value of the resulting spectral index is in both
cases 0.66+-0.07. Comparing radio properties of the maser galaxies with a
sample of Seyferts without detected H2O maser, we find that (1) the spectral
indices agree within the error limits, and (2) maser host galaxies have higher
nuclear radio continuum luminosities, exceeding those of the comparison sample
by factors of order 5. Only considering the subsample of galaxies with masers
associated with AGN, there seems to be a trend toward rising maser luminosity
with nuclear radio luminosity (both at 6 cm and 20 cm). However, when
accounting for the Malmquist effect, the correlation weakens to a level, which
is barely significant. Overall, the study indicates that nuclear radio
luminosity is a suitable indicator to guide future AGN maser searches and to
enhance detection rates, which are otherwise quite low (<10%).
