Washington: Scientists, including those of Indian origin, have identified the farthest gamma-ray blazars, a type of galaxy whose intense emissions are powered by supersized black holes, by using NASA’s Fermi Gamma-ray Space Telescope.
Light from the most distant object began its journey to us when the universe was 1.4 billion years old, or nearly 10 per cent of its present age.
“Despite their youth, these far-flung blazars host some of the most massive black holes known,” said Roopesh Ojha, an astronomer at NASA’s Goddard Space Flight Centre in the US.
“That they developed so early in cosmic history challenges current ideas of how supermassive black holes form and grow, and we want to find more of these objects to help us better understand the process,” Ojha said.
Blazars constitute roughly half of the gamma-ray sources detected by Fermi’s Large Area Telescope (LAT).
Astronomers think their high-energy emissions are powered by matter heated and torn apart as it falls from a storage, or accretion, disk toward a supermassive black hole with a million or more times the Sun’s mass.
A small part of this infalling material becomes redirected into a pair of particle jets, which blast outward in opposite directions at nearly the speed of light.
Blazars appear bright in all forms of light, including gamma rays, the highest-energy light, when one of the jets happens to point almost directly toward us.
Researchers led by Vaidehi Paliya and Marco Ajello at Clemson University in South Carolina began by searching for the most distant sources in a catalogue of 1.4 million quasars, a galaxy class closely related to blazars.
Since only the brightest sources can be detected at great cosmic distances, they then eliminated all but the brightest objects at radio wavelengths from the list.
With a final sample of about 1,100 objects, the scientists then examined LAT data for all of them, resulting in the detection of five new gamma-ray blazars.
The light we now detect from them started on its way when the universe was between 1.9 and 1.4 billion years old, researchers said.
“Once we found these sources, we collected all the available multiwavelength data on them and derived properties like the black hole mass, the accretion disk luminosity, and the jet power,” said Paliya.
Two of the blazars boast black holes of a billion solar masses or more. All of the objects possess extremely luminous accretion disks that emit more than two trillion times the energy output of our Sun.
This means matter is continuously falling inward, corralled into a disk and heated before making the final plunge to the black hole.
The study was published in The Astrophysical Journal Letters.
PTI
