Super Giant Black Hole In Regular Size Galaxy Is Rule Breaker

A gargantuan black hole that is one of the most massive black holes ever observed has been discovered inside of a normal size galaxy. The majority of black holes have small mass compared with their host galaxy.

The black hole, found by Benny Trakhtenbrot, of ETH Zurich’s Institute for Astronomy, along with an international team of astrophysicists, was formed back in the early universe, around two billion years after the Big Bang.

Located in the galaxy CID-947, it has a mass of almost 7 billion solar masses. One solar mass is equal to the mass of our sun.

But that wasn’t what surprised researchers the most. It was galaxy CID-947’s mass.

“The measurements correspond to the mass of a typical galaxy,” says Trakhtenbrot, a postdoctoral fellow. “We therefore have a gigantic black hole within a normal size galaxy.”

Our own Milky Way, along with most other galaxies, features a black hole at it’s center, comprised of millions to billions of solar masses. The new finding challenges existing ideas about the way host galaxies grow in relation to black holes.

Furthermore, previous studies suggested that the radiation emitted in the growth of the black hole controlled, or even halted, the creation of stars, as the released energy heated up the gas. These new results, however, imply the processes function differently, or at least did in the early universe.

The far-way young black hole seen by Trakhtenbrot and team had approximately 10 times less mass than its galaxy. In today’s local universe, black holes typically reach a mass of 0.2 to 0.5 percent of their host galaxy’s mass.

“That means this black hole grew much more efficiently than its galaxy—contradicting the models that predicted a hand-in-hand development,” Trakhtenbrot said.

Benny Trakhtenbrot1, C. Megan Urry, Francesca Civano, David J. Rosario, Martin Elvis, Kevin Schawinski, Hyewon Suh, Angela Bongiorno, Brooke D. Simmons
An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang
Science 10 July 2015: Vol. 349 no. 6244 pp. 168-171 DOI: 10.1126/science.aaa4506

Illustration: M. Helfenbein, Yale University/OPAC