How did the largest black holes get so big?

Chuck Bednar for – @BednarChuck

Quasars, the ravenous supermassive black holes that consume tremendous amounts of gas and dust into their gravitational pull, may be better at devouring matter than previously believed, according to research published in The Astrophysical Journal.

Using data obtained from the NASA Chandra X-ray Observatory, lead investigator Bin Luo, a postdoctoral researcher at Penn State University, and his colleagues examined 51 quasars located between five billion and 11.5 billion light years from Earth.

By discovering that that some quasars are consuming more matter than previous expected, the study authors believe that they could learn more about how these black holes were able to grow so rapidly during the earliest days of the universe. Luo said that the largest black holes appear to be consuming matter at rates five to ten time faster than most quasars.

Findings could explain early-universe black holes

The quasars were selected because they had unusually weak emission from atoms such as carbon at ultraviolet wavelengths, the agency explained in a statement. About two-thirds of those quasars were as fainter in X-rays than regular quasars, with some up to 40 times fainter.

Those weak UV atomic emissions and X-ray fluxes from these objects may help explain how a supermassive black hole consumes matter, NASA officials added. In computer models, experts found that as matter swirls towards a black hole in a thin disk when inflow rates are low, and if those inflow rates increase, pressure from radiation can dramatically inflate that disk.

Black holes can’t stop eating donuts

As a result of that inflation, a donut-shaped ring or “torus” can form around the inner part of the disk, the researchers found. If a quasar becomes embedded in this type of structure, the torus can absorb much of the radiation produced closer to the black hole, preventing it from colliding with gas located further out, resulting in weaker UV atomic and X-ray emissions.

The phenomenon would also affect the delicate balance between the inward pull of gravity and the outward pressure of radiation, the researchers said. An increased amount of radiation would be emitted perpendicular to the disk instead of along it, allowing material to be consumed at a higher rate.

“The important implication is that these ‘thick-disk’ quasars may harbor black holes growing at an extraordinarily rapid rate,” NASA noted. When combined with previous research, the new paper suggests that “quasars might have been more common” about one billion years after the Big Bang, and that this rapid growth “might also explain the existence of huge black holes at even earlier times,” they added.


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