No Evidence for Intermediate-Mass Black Holes in Globular Clusters:   Strong Constraints from the JVLA
  With a goal of searching for accreting intermediate-mass black holes (IMBHs), we report the results of ultra-deep Jansky VLA radio continuum observations of the cores of three Galactic globular clusters: M15, M19, and M22. We reach rms noise levels of 1.5-2.1 uJy/beam at an average frequency of 6 GHz. No sources are observed at the center of any of the clusters. For a conservative set of assumptions about the properties of the accretion, we set 3-sigma upper limits on IMBHs from 360-980 M_sun. These limits are among the most stringent obtained for any globular cluster. They add to a growing body of work that suggests either (a) IMBHs ~> 1000 M_sun are rare in globular clusters, or (b) when present, IMBHs accrete in an extraordinarily inefficient manner. 
Jay Strader, Laura Chomiuk, Thomas Maccarone, James Miller-Jones, Anil   Seth, Craig Heinke, Gregory Sivakoff
astro-ph.HE astro-ph.CO astro-ph.GA