Event Details

CATEGORY:Conference Lecture
Date: 2012-05-28
Time: 12:30:00
Location: Lidow, Asher Peres (502)


First and most reliably discovered in ground-based observations, supermassive black holes (BHs) have now been found in ~65 galaxies with the Hubble Space Telescope (HST) and with other facilities.  HST revolutionized BH research by advancing the subject from its "proof of concept" phase into quantitative studies of BH demographics. Most influential was the discovery of a tight correlation between BH masses and the velocity dispersion of stars in the host galaxy bulge component at radii where the stars mostly feel each other and not the BH.  Together with correlations between MBH and bulge luminosity, with the "missing light" that defines galaxy cores, and with numbers of globular clusters, this has led to the fundamental conclusion that BHs and bulges "co-evolve" and perhaps regulate each other's growth.  This simple picture with one set of correlations for all galaxies dominated BH work in the past decade. New results are now replacing the above, simple story with a richer and more plausible picture in which BHs correlate differently with different kinds of galaxy components.  A reasonable aim is to use this progress to refine our understanding of how BHs grow and interact with galaxies.  We now know that BHs with masses of 10**5 to 10**6 solar masses live in at least some bulgeless galaxies.  Therefore, classical (merger-built) bulges are not necessary equipment for BH formation.  On the other hand, while they live in galaxy disks, BHs do not correlate with galaxy disks or with disk-grown pseudobulges.  They also do not correlate with dark matter halos.   This leads to the suggestion that there are two modes of BH feeding, global feeding in galaxy mergers that leads to giant BHs that correlate with host ellipticals, and local and more stochastic feeding of small BHs in largely bulgeless galaxies that evidently involves too little energy feedback to engineer BH-host coevolution.  Investigating coevolution continues to be a major growth industry.