Megamaser disks provide the most precise and accurate extragalactic supermassive black hole masses .
Here we describe a search for megamasers in nearby galaxies using the Green Bank Telescope ( GBT ) .
We focus on galaxies where we believe that we can resolve the gravitational sphere of influence of the black hole and derive a stellar or gas dynamical measurement with optical or NIR observations .
Since there are only a handful of super massive black holes ( SMBH ) that have direct black hole mass measurements from more than one method , even a single galaxy with a megamaser disk and a stellar dynamical black hole mass would provide necessary checks on the stellar dynamical methods .
We targeted 87 objects from the Hobby-Eberly Telescope Massive Galaxy Survey , and detected no new maser disks .
Most of the targeted objects are elliptical galaxies with typical stellar velocity dispersions of 250 km s ^ { -1 } and distances within 130 Mpc .
We discuss the implications of our non-detections , whether they imply a threshold X-ray luminosity required for masing , or possibly reflect the difficulty of maintaining a masing disk around much more massive ( \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 4.0 pt \hbox { $ \sim$ } } } \hbox { \raise 2. % 0 pt \hbox { $ > $ } } } } 10 ^ { 8 } M _ { \odot } ) black holes at low Eddington ratio .
Given the power of maser disks at probing black hole accretion and demographics , we suggest that future maser searches should endeavour to remove remaining sample biases , in order to sort out the importance of these covariant effects .