NASA’s Fermi Gamma-Ray Space Telescope has spotted the five most distant gamma-ray blazars — a type of galaxy whose intense emissions are powered by supermassive black holes — yet known.
In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light. For active galaxies classified as blazars, one of these jets beams almost directly toward Earth. Image credit: NASA / Goddard Space Flight Center Conceptual Image Lab.
Blazars constitute roughly half of the gamma-ray sources detected by the Large Area Telescope (LAT), the principal scientific instrument on the Fermi spacecraft.
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.
“High-redshift blazars detected by LAT are of great astrophysical importance as they are extreme objects whose energetics remain a mystery,” said Dr. Roopesh Ojha of NASA’s Goddard Space Flight Center and co-authors.
“Such blazars are intrinsically interesting since they inform us about the evolution of gamma-ray blazars and are, by definition, some of the more luminous blazars in the LAT sample.”
“These blazars appear to host very massive black holes and could shed light on the origin and growth of black holes in the early Universe.”
Dr. Ojha and his colleagues searched for the most distant sources in a catalog of 1.4 million quasars.
Because only the brightest sources can be detected at great cosmic distances, the astronomers then eliminated all but the brightest objects at radio wavelengths from the list.
With a final sample of about 1,100 objects, they then examined LAT data for all of them, resulting in the detection of five new gamma-ray blazars: J064632+445116, J151002+570243, J135406-020603, J163547+362930 and J212912-153841.
“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,” explained Dr. Vaidehi Paliya of Clemson University.
Expressed in terms of redshift, the newly-discovered blazars range from redshift 3.3 to 4.31, which means the light we now detect from them started on its way when the Universe was between 1.9 and 1.4 billion years old, respectively.
The most distant object, J151002+570243, emitted its light when the Universe was just one-tenth its current age. This blazar hosts a black hole with a mass of 3 billion solar masses. Another of these distant blazars boasts a black hole more than twice this size.
All of the objects possess extremely luminous accretion disks that emit more than two trillion times the energy output of the Sun. This means matter is continuously falling inward, corralled into a disk and heated before making the final plunge to the black hole.
“The main question now is how these huge black holes could have formed in such a young Universe. We don’t know what mechanisms triggered their rapid development,” said Dr. Dario Gasparrini of the Italian Space Agency’s Science Data Center.
The astronomers presented their findings January 30, 2017 at the APR17 Meeting of the American Physical Society in Washington, DC.
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Roopesh Ojha et al. 2017. Expanding the Gamma-ray Universe: High Redshift Fermi-LAT Blazars. APR17 Meeting of the American Physical Society, abstract # S4.00008
This article is based on a press-release from NASA.
