  The stellar mass binary black hole (sBBH) mergers presently detected by LIGO
may originate wholly or in part from binary black hole mergers embedded in
disks of gas around supermassive black holes. Determining the contribution of
these active galactic nucleus (AGN) disks to the sBBH merger rate enables us to
uniquely measure important parameters of AGN disks, including their typical
density, aspect ratio, and lifetime, thereby putting unique limits on an
important element of galaxy formation. For the first time, gravitational waves
will allow us to reveal the properties of the hidden interior of AGN disks,
while electromagnetic radiation (EM) probes the disk photosphere. The
localization of sBBH merger events from LIGO is generally insufficient for
association with a single EM counterpart. However, the contribution to the LIGO
event rate from rare source types (such as AGNs) can be determined on a
statistical basis. To determine the contribution to the sBBH rate from AGNs in
the next decade requires: {\em 1) a complete galaxy catalog for the LIGO search
volume, 2) strategic multi-wavelength EM follow-up of LIGO events and 3)
significant advances in theoretical understanding of AGN disks and the behavior
of objects embedded within them.}
