Special Astrophysics Seminar

Giant black holes in clusters of galaxies

Julie Hlavacek-Larrondo

Stanford University

One of the most fascinating discoveries in modern astrophysics has been the realization that all massive galaxies must harbour a black hole at their centres, and that these black holes can be colossal (M_BH>10⁶ Msun). The interplay between the accretion of material and the release of energy of one of these black holes is known as AGN feedback, and during this talk, I will review the status of this field while concentrating on the most massive black holes in the Universe, those that lie at the centres of clusters of galaxies. I will also present new results suggesting that some of these black holes are significantly more massive than previously thought, i.e. that some are ultramassive (M_BH>10¹⁰ Msun) as opposed to supermassive (M_BH~10⁹ Msun). The existence of ultramassive black holes puts stringent constraints on black hole formation models as it remains unclear how black holes can grow to such masses.