Home > Astronomy, Black Holes, Galaxies, General Astronomy > Galaxy Interactions Help Grow Big Black Holes

Galaxy Interactions Help Grow Big Black Holes


Supermassive black holes (SMBH) sit at the center of most galaxies that we observe today. How did they grow to millions or billion times the mass of our Sun? Answers to this question have been elusive for some time although important clues have been uncovered. For instance, SMBHs prefer to reside in the most massive galaxies and the mass of a SMBH is directly related to the mass of stars present in the central region (i.e., bulge) of its host galaxy. It is now thought that such massive galaxies grew in part by mergers and interactions between less massive galaxies. Such violent episodes in the evolution of galaxies have also been invoked to explain how matter is driven to their center that can then grow a SMBH.

A simple test is to determine whether SMBHs are found in greater numbers in galaxies undergoing a merger compared to those in isolation. While this sounds easy enough, astronomers have struggled to effectively carry out this test for some time. This is because the glaring light of an actively growing SMBH, seen observationally as either an active galactic nucleus (AGN) or the more luminous quasar, can outshine their entire host galaxy making it difficult to determine whether they reside in a galaxy undergoing an interaction with another fainter galaxy. Such interactions should distort the shape of the galaxy.

Full Story: http://www.ipmu.jp/node/1156

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