Article Summary #10

Dark matter haloes determine the masses of supermassive black holes

C. M. Booth, Joop Schaye, 2009, eprint arXiv:0911.0935
http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:0911.0935

Suppermassive Black Holes (SMBH) are found in the center of most massive galaxies and the characteristics of the black holes are known to be strongly related to its host galaxy.

Black holes, as described by general relativity, are a region of space from which nothing can escape, not even light. It is a very compact and massive object that is know to deform space and time and they receive their mass through the accretion of matter around them. The material accelerates during its fall into the black hole, becomes hotter and starts radiating in various energy ranges (depending on its temperature). This radiated energy is what causes the correlation between the black hole’s properties and those of the Galaxy.

It has bee discovered that SMBH are always gravitationally dominant and this is thought to be due to its ability to regulate the rate at which it accretes the matter around it (this phenomenon is called “self-regulation”). The luminous center of the galaxy is called the “bulge” and it is not clear whether the self-regulation occurs inside the bulge (i.e. <1 kpc), on the galaxy scale, or in the entire dark matter halo around the galaxy.

Their analysis is done through a simulation of a black hole and its host galaxy. The goal is finding the initial conditions that would result in a black hole-galaxy evolution to the current state and correlations observed. What was found was unexpected: the energy transferred from the black hole into the surrounding medium does not change when the fraction of the accreted rest mass energy is increased. Also, another result from the simulations is that it is not the stellar mass in the galaxy, but rather the mass of the dark matter halo that determines the mass of the black hole.