Monday, November 9 2009

We now know that supermassive black holes lurk in the centers of most bulge-dominated galaxies in the local Universe and that their black hole mass and the stellar velocity dispersion of their host galaxy are strongly correlated.  This discovery has launched numerous speculations that the formation and evolution of galaxies and supermassive black holes are fundamentally linked, perhaps as feedback from the active galactic nucleus regulates the surrounding star formation in the host galaxy.  However, an important outstanding question remains unresolved: Is a bulge in general necessary for a black hole to form and grow? The answer to this question has a profound impact on some key fundamental questions on the connection between black holes and galaxy formation and evolution that have yet to be answered such as: Which forms first in a galaxy, the black hole or the bulge? What is the origin, efficiency of formation, and mass scale of supermassive black hole seeds? Are interactions necessary for black holes to form and grow?  In this talk, I will summarize results from the first systematic mid-infrared spectroscopic search using Spitzer for active supermassive black holes in the centers of bulgeless galaxies.  I will discuss recent findings on the relationship between the host and black hole properties in galaxies without bulges.