Massive black holes may be quasar relics

U. MICHIGAN (US) — Two newly discovered black holes that are 10 billion times the mass of the sun—the largest ever found—may be the fossil remains of quasars from the early universe.

Black holes are dense concentrations of matter that produce such strong gravitational fields that not even light can escape. These new ones are at the centers of two elliptical galaxies more than 300 million light years from Earth.

Quasars, the brightest objects in the universe, are active galaxy cores—glowing gas and dust just beyond the reach of a central supermassive black hole. When their fuel runs out, quasars go dim, leaving behind black holes.

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Scientists say the discovery, reported in the journal Nature, confirms their understanding of quasars’ life cycle.

“The most luminous quasars seem to require a black hole of 10 billion solar masses to provide the amount of energy being radiated. For a long time, we weren’t finding any black holes that large, says Douglas Richstone, professor of astronomy at the University of Michigan. “Now it turns out that they are there, and the theory fits together with the observations.”

Approximately 63 supermassive black holes have been found at the cores of nearby galaxies. The largest for over three decades was a 6.3-billion solar mass black hole in the center of the nearby galaxy M87.

One of the newly discovered black holes is 9.7 billion solar masses and is located in the elliptical galaxy NGC 3842, which is the brightest galaxy in the Leo cluster 320 million light years away in the direction of the constellation Leo. The second is as large or larger and sits in the elliptical galaxy NGC 4889, which is the brightest galaxy in the Coma cluster about 336 million light years from Earth in the direction of the constellation Coma Berenices.

“These black holes may shed light on how black holes and their surrounding galaxies have nurtured each other since the early universe,” says Nicholas McConnell a graduate student at the University of California, Berkeley, who is first author of the paper.

Understanding the early universe is about understanding our own origins, Richstone says. “We can see the microwave background radiation in the universe, left over from the Big Bang. It’s very smooth. There are ripples in it, but they’re low-amplitude. Everything we know and love in the universe—stars, planets, black holes, people—grows out of these small perturbations.

“Understanding that process is a big part of the agenda of modern astronomy. And understanding how supermassive black holes form and correlate with their host galaxy and how those galaxies form is an early part of that story.”

Scientists from the University of Texas, University of Toronto, and the National Optical Astronomy Observatory contributed to the research that was funded by the National Science Foundation, NASA, and UC Berkeley’s Miller Institute for Basic Research in Science.

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