The black hole mass-galaxy age relation

We present evidence that there is a significant correlation between the fra ction of the mass of a galaxy that lies in its central black hole and the a ge of the galactic stellar population. Since the absorption-line indices th at are used to estimate the age are luminosity-weighted, they essentially m easure the time since the last significant episode of star formation in the galaxy. The existence of this correlation is consistent with several theor ies of galaxy formation, including the currently favoured hierarchical pict ure of galaxy evolution, which predicts just such a relation between the bl ack hole mass and the time since the last burst of merger-induced star form ation. It is not consistent with models in which the massive black hole is primordial, and hence uncoupled from the stellar properties of the galaxy.