  Intermediate mass black holes have been alternatively predicted to be quite
common in the centers of globular clusters or nearly impossible to form and
retain in the centers of globular clusters. As it has been recently shown that
radio observations are currently the most sensitive observational technique for
detecting such objects, we have obtained new deep radio observations of Omega
Cen, and have re-analyzed older observations of M~15 in hope of constraining
the masses of possible black holes in their centers. In both cases, upper
limits of about 100 $\mu$Jy are found at GHz frequencies. We find that if the
Bondi-Hoyle accretion rate truly represents the spherical accretion rate onto a
black hole, then the masses of the black holes in the centers of these two
galaxies are severely constrained - with mass limits of less than about 100
solar masses in both cases. If more realistic assumptions are made based on
recent work showing the Bondi rate to be a severe overestimate, then the data
for Omega Cen are marginally consistent with a black hole of about 1/1000 the
cluster's mass (i.e. about 1000 $M_\odot$). The data for M~15 then are only
marginally consistent with previous reports of a $\sim2000$ solar mass black
hole, and we note that there is considerable hope for either detecting the
black hole or improving this upper limit with current instrumentation. Finally,
we discuss the possibility that the radio source near the core of the Ursa
Minor dwarf spheroidal galaxy is a $\sim10^4$ $M_\odot$ black hole.

Astrophysics