'Quasars' dining on more cosmic matter than first thought at excessive rates

A new study using NASA's Chandra X-ray Observatory has suggested that a group of unusual giant black holes may be consuming excessive amounts of matter.

Astronomers have known for some time that supermassive black holes can gobble up huge quantities of gas and dust that have fallen into their gravitational pull. As the matter falls towards these black holes, it glows with such brilliance that they can be seen billions of light years away. Astronomers call these extremely ravenous black holes "quasars."

The result suggests that some quasars are even more adept at devouring material than scientists previously knew and this finding may help them understand how the largest black holes were able to grow so rapidly in the early Universe.

Lead researcher Bin Luo of Penn State University stated that even for famously prodigious consumers of material, these huge black holes appear to be dining at enormous rates, at least five to ten times faster than typical quasars.

Luo and his colleagues examined data from Chandra for 51 quasars that are located at a distance between about 5 billion and 11.5 billion light years from Earth. These quasars were selected because they had unusually weak emission from certain atoms, especially carbon, at ultraviolet wavelengths. About 65 percent of the quasars in this new study were found to be much fainter in X-rays, by about 40 times on average, than typical quasars.

The weak ultraviolet atomic emission and X-ray fluxes from these objects could be an important clue to the question of how a supermassive black hole pulls in matter. Computer simulations show that, at low inflow rates, matter swirls toward the black hole in a thin disk. However, if the rate of inflow is high, the disk can puff up dramatically, because of pressure from the high radiation, into a torus or donut that surrounds the inner part of the disk.

The important implication is that these "thick-disk" quasars may harbor black holes growing at an extraordinarily rapid rate. The current study and previous ones by different teams suggest that such quasars might have been more common in the early Universe, only about a billion years after the Big Bang. Such rapid growth might also explain the existence of huge black holes at even earlier times.

The results appear in The Astrophysical Journal.