Lonely Galaxy Spotted by Chandra in Cluster That Should Hold Many, But Why Is It Alone?

A galaxy called 3C 297 was spotted to be alone, despite its environment suggesting that it should be part of a galaxy cluster of around a hundred galaxies.

Lonely Galaxy

Science Alert reports that the fact that galaxy 3C 297 is drifting alone suggests that something must have happened to its surrounding galaxies. Valentina Missaglia, an astronomer from the University of Torino in Italy, says that it seems that the galaxy cluster that 3C 297 is part of is missing almost all of the galaxies within it. While they expected to find over a dozen galaxies that are as big as the Milky Way, they only spotted one.

The galaxy's environment was studied through data from the Chandra X-ray Observatory, which looks at high-energy radiation that comes from strong sources in the universe. NASA reports that this lonely galaxy is located around 9.2 billion light years away from earth. It holds a supermassive hole within it that pulls in gas at its center and ejects strong jets that reflect as radio waves.

Galaxy 3C 297 Is Part of a Galaxy Cluster

Missaglia and colleagues were able to notice two key characteristics of a galaxy cluster in the data from the Chandra X-ray. First, they discovered that the lonely galaxy is engulfed by gas that has extremely high temperatures that go as high as tens of millions of degrees. This is something that is typically observed in galaxy clusters.

Secondly, the jet of the supermassive black hole has created an x-ray source that is roughly 140,000 light years away. This implies that it has worked through the galaxy's surrounding gas.

The galaxy possesses a third trait, which was previously reported from data from the Karl G. Jansky Very Large Array. The galaxy has a bent radio jet, which signifies that it has had prior interactions with its surroundings.

The team observed that no galaxy, out of 19, that looks close to 3C 297 in an optical image is actually the same distance as 3C 297. Now, what could have happened to the other galaxies within the cluster?

Why Is the Galaxy 3C 297 Alone?

Juan Madrid, a co-author of the study who is from the University of Texas, says that they think that the gravitational pull of a huge galaxy mixes with strong interactions across galaxies. They then merged with the big one. For such galaxies, resistance appeared to be futile.

Considering its lonely state, the researchers think that 3C 297 is not a galaxy cluster anymore but a fossil group. This is the ending phase of a galaxy that pulls in and combines with other celestial bodies. Though several fossil groups have been spotted before, 3C 297 is quite distant.

Mischa Schirmer, one of the study's co-authors who is from the Max Planck Institute for Astronomy, says that it is quite difficult to explain how the cosmos is capable of making such a system just 4.6 billion years post-Big Bang. While it does not conflict with current concepts in cosmology, it pushes the limits on how fast galaxy clusters and galaxies could have formed.

While the authors cannot disregard dwarf galaxies that may surround 3C 297, the presence of such galaxies will not explain the absence of bigger celestial bodies.

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