A multinational team of astronomers has spotted an oversized black hole in the center of a typical star-forming galaxy, called CID-947.
This illustration shows a black hole that grew faster than its host galaxy. Image credit: Michael S. Helfenbein / Yale University.
CID-947’s black hole was originally discovered using NASA’s Hubble Space Telescope, and was then detected in the Sloan Digital Sky Survey and by ESA’s XMM-Newton and NASA’s Chandra X-ray Observatory.
Dr Benny Trakhtenbrot of ETH Zurich’s Institute for Astronomy in Switzerland and his colleagues performed a follow-up observation of the object using the 10-m Keck telescope in Hawaii.
According to the team, the black hole in the center of CID-947 is among the most massive black holes discovered up to now. It measures nearly 7 billion solar masses, and formed in the early Universe, around 2 billion years after the Big Bang.
What surprised the astronomers in particular was not the black hole’s record mass, but rather the galaxy’s mass.
“The measurements correspond to the mass of a typical galaxy. We therefore have a gigantic black hole within a normal-size galaxy,” said Dr Benny Trakhtenbrot of ETH Zurich’s Institute for Astronomy in Switzerland, lead author of a paper published in the journal Science (arXiv.org preprint).
The distant black hole had roughly 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,” Dr Trakhtenbrot said.
The astronomers also concluded from their observations that although the black hole had reached the end of its growth, stars were still forming. Contrary to previous assumptions, the energy and gas flow, propelled by the black hole, did not stop the creation of stars.
“Stars were still forming in CID-947 and the galaxy could continue to grow,” the scientists said.
“CID-947 could be a precursor of the most extreme, massive systems observed in today’s local Universe, such as the galaxy NGC 1277 in the Perseus constellation, 220 million light years from the Milky Way.”
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Benny Trakhtenbrot et al. 2015. An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang. Science, vol. 349, no. 6244, pp. 168-171; doi: 10.1126/science.aaa4506
