Deep in the Cosmic Forest, a Black Hole Goldilocks Might Like
There is a suggestive correlation between the mass of a galaxy and the mass of the black hole in its center: The bigger the galaxy, the bigger its hole. This has led astronomers to a rough theory of how the universe gets built in the dark: Small galaxies with their “small” holes accrete into bigger and bigger assemblages of stars, with ever-bigger black holes at the center of it all. Intermediate-mass black holes, weighing hundreds or tens of thousands of solar masses, could be expected to anchor the centers of smaller dwarf galaxies. But as such they would be hard to find. We only notice black holes when they feed. Stellar-size black holes call attention to themselves as they cannibalize their companions in double star systems. Their supergiant cousins feed at troughs at the centers of big galaxies. But intermediate black holes living in dwarf galaxies would normally find little to eat.