A group of astronomers, including scientists from the state of Penn, have announced the discovery of a highly hidden black hole that exists only 850 million years after the Big Bang . using NASA's Chandra X-ray Observatory. This is the first indication of a hidden black hole at such an early date.
Super-sized black holes usually grow by sucking material from a disk of surrounding matter. For the fastest growth, this process creates a tremendous amount of radiation in a very small area around the black hole and creates an extremely bright, compact source called quasar.
Theoretical calculations indicate that most of the early growth of black holes is present, while the black hole and the disk are surrounded by a dense gas cloud that feeds material into the disk. As the black hole grows, the gas in the cloud is exhausted until the black hole and its bright disc are exposed.
"It is extremely difficult to find quasars in this hidden phase because so much of their radiation is absorbed and can not be detected by current instruments," said Fabio Vito, CAS-CONICYT Fellow at the Pontificia Universidad Católica de Chile who led the study he began as a postdoctoral fellow at Penn State. "Thanks to Chandra and X-ray's ability to penetrate the dark cloud, we believe we finally made it."
The discovery came from observations of a quasar called PSO 167-13, first discovered by Pan-STARS, an optical telescope in Hawaii. Optical observations from these and other studies have led to the discovery of about 200 quasars that were already bright when the universe was less than a billion years old or about 8 percent of its present age. These studies were only effective in finding unobstructed black holes, as the radiation they perceived was suppressed by even thin clouds of surrounding gas and dust. Therefore, it was expected that PSO 167-13 remained unobserved.
Vito's team was able to test this idea by making Chandra observations of PSO 167-13 and nine other quasars through optical surveys. After 16 hours of observation, only three x-ray photons with relatively high energies were detected from PSO 167-13. Low energy x-rays are more easily absorbed than higher energy x-rays. The probable explanation for the Chandra observation is that the quasar is heavily occluded by gas and only high energy x-rays can be detected.
"This was a complete surprise," said co-author Niel Brandt, Verne M. Willaman, a professor of astronomy and astrophysics and a professor of physics at Penn State. "It was like waiting for a moth, but seeing a cocoon instead. None of the other nine quasars we observed were disguised as we expected.
An interesting twist for PSO 167-13 according to the researchers is that the galaxy hosting the quasar has a close companion galaxy previously seen in data obtained with the Atacama Large Millimeter Array ( ALMA ) of radio equipment in Chile and the NASA Hubble Space Telescope. Due to the tight separation and weakness of the X-ray source, the team was unable to determine whether the newly discovered X-ray emission was related to the Quasar PSO 167-13 or the companion galaxy.
If the X rays originate from the well-known quasar, then astronomers must develop an explanation of why the quasar appeared strongly concealed in X-rays but not in optical light. One possibility is that the occlusion of the quasar in the three years between optical and X-ray observations has increased rapidly and rapidly.
If the x-rays come from instead The companion galaxy then represents the discovery of a new quasar in the immediate vicinity of PSO 167-13. This quasar pair would be the most distant yet and would break the record of 1.2 billion years after the big bang. In both cases, the quasar discovered by Chandra would be the farthest one yet seen. The previous record holder is observed 1.3 billion years after the Big Bang. The authors plan to further characterize the source by subsequent observations.
"With a longer Chandra observation, we can get a better estimate of how obscured this black hole is," said co-author Franz Bauer, also from the Pontificia Universidad Católica de Chile and a former Penn State postdoctoral fellow, " The x-ray source safely identifies with the well-known quasar or companion galaxy. "
The authors are also planning to look for other examples of heavily obscured black holes.
"We suspect that the majority of supermassive black holes are hidden in the early universe: it is then crucial to recognize and study them to understand how they could grow into masses of one billion suns so fast", said co-author Roberto Gilli of INAF in Bologna, Italy.
An article describing these results appears online in the journal Astronomy and Astrophysics.
NASA's Marshall Space Flight Center ma supports the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls the science and operations of Cambridge, Massachusetts. The data used in this study was collected using the Advanced CCD Imaging Spectrometer on Chandra, an instrument designed and designed by a team led by Penn State Evan Pugh, Professor Emeritus of Astronomy and Astrophysics, Gordon Garmire.
In addition to Bauer's Vito, Brandt, and research team, former postdoctoral researchers include Ohad Shemmer, Cristian Vignali, and Bin Luo, who also earned their doctorate at Penn State.