deletions | additions       diff --git a/h2o_megamasers.tex b/h2o_megamasers.tex  index 5801a71..2eaf119 100644  --- a/h2o_megamasers.tex  +++ b/h2o_megamasers.tex 
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\citet{wardle2012_bhmass} have derived a model for the formation of these circumnuclear disks around AGN. They argue that impacts of molecular clouds, within some impact parameter, can cause the formation of a thin Keplerian disk. By equating the specific angular momentum at the edge of the disk to that of the material that can just barely be captured by the interaction, they find a relation between the radius of the circumnuclear disk and the mass of the SMBH: $R=4G\lambda^2M/v^2$, where $\lambda$ is the fraction of angular momentum maintained in the interaction, $M$ is the SMBH mass, and $v$ is the initial velocity of the cloud. They find that the relation holds for eight disks with H$_2$O mega-maser emission, largely within observational error. They suggest that the impact of a cloud on one of these disks could create gravitationally unstable episodes, which may potentially give rise to mega-maser emission \citep{Milosavljevi_2004} such that only a fraction host Keplerian circumnuclear disks.  {\bf XXX Constraining low The precision of these SMBH  mass measurements enable their use for constraining the low  end of M-sigma the $M_{\mathrm{BH}}-\sigma$ relation, where $\sigma$ is the velocity dispersion of stars in the bulge. The high-end of this  relation XXX} is well-constrained based on mass measurements in  % \begin{itemize}  % \item greene+2013, Wardle Yusef-zadeh 12, greene+10, schulz henkel 03, tarchi+12  % \item rotation curves implied by the disk (and the small compact scales involved) give direct measurement of the SMBH masses  % \item greene+10 model the maser rotation curves to derive BH masses; use SDSS to derive stellar velocity dispersions -- to very high precision!! (<15\%)  % \item find that maser galaxies fall below the $M_BH-\sigma$ relation defined for ellipticals -- the relation cannot be used to derive the BH mass function for AGN -- NO UNIVERSAL power-law MBH-sigma relation  % \item Find M_BH relates to properties of the bulge, but not strongly with overall galactic luminosity