An article published in the journal “Astronomy & Astrophysics” reports the discovery of a supermassive black hole in an initial phase of growth in which it’s heavily obscured and that dates back to around 850 million after the Big Bang, the oldest of that type discovered so far. A team of researchers used data collected by NASA’s Chandra X-ray Observatory to carry out this study but even putting together other data collected with the ALMA radio telescope it’s not certain whether that black hole matches the quasar cataloged as PSO167-13 or a nearby galaxy.
The discovery of a primordial supermassive black hole is nothing new but generally they get detected when they’re surrounded by considerable amounts of materials that are heated to the point of emitting electromagnetic radiation even in the form of X-rays in an activity known as a quasar. However, there’s a phase during a quasar’s growth in which the black hole that powers it is surrounded by materials that are contributing to its growth but are also obscuring what happens in its vicinity at many electromagnetic frequencies, making its sighting more difficult.
The Chandra X-ray Observatory allows the detection of X-rays that can pass through the gas and dust that surround a highly obscured supermassive black hole and a team led by Fabio Vito of the Pontificia Universidad Católica de Chile found one by analyzing the data of various observations conducted with that NASA’s space telescope. However, the result isn’t yet conclusive because there are still doubts about the real source of that activity as it could be the quasar PSO 167-13 but some time ago the ALMA radio telescope allowed to identify a galaxy close to it that could be an obscured quasar.
If the obscured quasar is really PSO 167-13 it remains to understand why it was already known after being seen at optical frequencies as well. One possibility is that in the three years that passed since the optical observations, it got obscured. If instead the obscured quasar is PSO 167-13’s neighbor the two objects would form the most distant quasars pair detected so far.
Image (X-ray: NASA/CXO/Ponticifca Catholic Univ. of Chile/F. Vito; Radio: ALMA (ESO/NAOJ/NRAO); Optical: PanSTARRS) shows an image from the PanSTARRS survey at optical frequencies with the position of the obscured supermassive black hole at the center, identified by a red cross. In that position there are the quasar PSO 167-13, shown at X-rays in blue in one of the insets, and the neighboring galaxy, shown in red at radio wavelengths in the other inset.
It took 16 hours of observations with Chandra to detect three X-ray photons, all at rather high energies, from the obscured supermassive black hole. This gives an idea of how difficult it is to discover these objects so far away in that phase of their growth.
Roberto Gilli of the Italian National Institute of Astrophysics, Bologna, one of the authors of the research, stated that he and his colleagues suspect that most supermassive black holes in the primordial universe are hidden and that finding and studying them can enable them to understand how they can grow so rapidly until they reach masses that can even be billions of times the Sun’s. For this reason, the researchers intend to look for more examples of heavily obscured supermassive black holes.