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Astronomers Have Found The Farthest Cloaked Super-massive Black Hole Yet

Credit: X-ray: NASA/CXO/Ponticifca Catholic Univ. of Chile/F. Vito; Radio: ALMA (ESO/NAOJ/NRAO); Optical: Pan-STARRS

Super-massive black holes are  located at the core of most galaxies. Some are known as quasars, who are emitting powerful jets in an active way, while others are quiet and idle. Then there are some active ones that get shrouded by huge clouds of gas, that is a possible sign, showing the early stages of a super-massive black hole turning bigger and entering its full quasar phase.

So far astronomers have already found the farthest “cloaked” super-massive black hole they think. In the field of astronomy, looking into the cosmos is just like looking back in time, the light from this object comes from when the universe was 830 million years old (just 6 percent of its current age). The discovery was released in recent edition of the journal Astronomy & Astrophysics.

The object was known as  PSO167-13, being part of a group of quasars previously identified three years ago. With help of the Chandra X-ray observatory, the astronomers followed up by conducting routine investigations on this and another nine quasars. They assumed that the quasars were not all obscured, because they had been already detected in visible light, however the X-rays offered another kind of explanation.  

After 16 hours of observations, the scientists could only detect three X-ray photons for PSO167-13 and these were all relatively high energy X-ray astronomers are used to a low number of photons, but the characteristics of this detection was giving a lead that something else was happening. The low-energy X-ray emissions, which should be present in a quasar, were missing. For this reason, the researchers thinks the quasar is cloaked.  

As Mr Fabio Vito, from the Pontificia Universidad Católica de Chile, said , it was a huge challenging task to discover quasars in this cloaked phase because so much of their radiation was absorbed and could not  be detected by current instruments. With assistance of Chandra and the ability of X-rays to pierce through the obscuring cloud, scientists were certain that they would finally succeed.  

As for the question that how quasar could go from being visible to cloaked in just three years, the researchers had two possible answers: one was that the black hole just received a large amount of gas, the another one was that they were spotting a nearby black hole. The galaxy hosting PSO167-13 had a companion, so either explanation might fit the bill.

In the eyes of Mr Franz Bauer, scientist also from the Pontificia Universidad Católica de Chile, with a longer Chandra observation, their team would be  able to get a better estimate of how obscured this black hole was and make a confident identification of the X-ray source with either the known quasar or the companion galaxy.

If it turned out to be from the companion, this would be the furthest quasar pair ever identified. The team were planing to search for more examples of these types of black holes. It was possible that cloaked supermassive black holes were not unusual in the early universe. Studying them might be much helpful for us to know better how they grew so exponentially fast during the first billion years of the cosmos.