Astronomers using NSF’s Very Long Baseline Array (VLBA) have found a quasar with the brightest radio emission ever observed in the early Universe.
Quasars are galaxies with supermassive black holes at their cores.
The powerful gravitational pull of such a black hole draws in nearby material, which forms a rotating disk around the massive object. The rapidly-spinning disk spews jets of particles moving outward at speeds approaching that of light. These energetic ‘engines’ are strong emitters of light and radio waves.
The newly-discovered quasar, called PSO J352.4034-15.3373 (P352-15 for short), is extremely bright in the radio part of the spectrum.
The extremely sharp radio vision of the VLBA showed P352-15 split into three major components, two of which show further subdivision. The components are spread over a distance of only about 5,000 light-years.
“This is the most detailed image yet of such a bright galaxy at this great distance,” said Dr. Emmanuel Momjian, of the National Radio Astronomy Observatory.
“There is a dearth of known strong radio emitters from the Universe’s youth and this is the brightest radio quasar at that epoch by a factor of 10,” added Dr. Eduardo Banados, from the Carnegie Institution for Science.
P352-15’s light has been traveling nearly 13 billion of the Universe’s 13.7 billion years to reach our planet.
“We are seeing P352-15 as it was when the Universe was less than a billion years old, or only about 7% of its current age,” said Dr. Chris Carilli, from the National Radio Astronomy Observatory and the Cavendish Laboratory at the University of Cambridge.
“This is near the end of a period when the first stars and galaxies were re-ionizing the neutral hydrogen atoms that pervaded intergalactic space.”
“Further observations may allow us to use this quasar as a background ‘lamp’ to measure the amount of neutral hydrogen remaining at that time.”
The three major components of P352-15 can be explained in one of two ways, according to the team.
One explanation is that they’re seeing the bright core of the quasar, corresponding to the location of the supermassive black hole itself, at one end, and the two other bright spots are parts of a one-sided jet.
The other possibility is that their middle object is the core, and the other objects are jets ejected in opposite directions. Because one of the end objects is closest to the position of the quasar as seen with visible-light telescopes, they consider the one-sided jet to be the more likely explanation.
The one-sided jet explanation raises the exciting possibility that astronomers may be able to detect and measure the expansion of the jet by observing P352-15 over several years.
“This quasar may be the most distant object in which we could measure the speed of such a jet,” Dr. Momjian said.
If, instead, the middle object is the core, with two oppositely-moving jets, its small size suggests that it may be very young or be embedded in dense gas that is slowing the jets’ expansion.
Planned future observations will tell which scenario is accurate.
“This quasar’s brightness and its great distance make it a unique tool to study the conditions and processes that prevailed in the first galaxies in the Universe. We look forward to unraveling more of its mysteries,” Dr. Carilli said.
Emmanuel Momjian et al. 2018. Resolving the Powerful Radio-loud Quasar at z ~ 6. ApJ 861, 86; doi: 10.3847/1538-4357/aac76f
Eduardo Bañados et al. 2018. A Powerful Radio-loud Quasar at the End of Cosmic Reionization. ApJL 861, L14; doi: 10.3847/2041-8213/aac511