Astronomers Discover a Surprisingly Lonely Galaxy

In the Universe, there is a galaxy, called 3C 297, that is more lonely than expected after having probably attracted and absorbed its previous companion galaxies. The galaxy is about 9.2 billion light years from Earth and contains a quasar, a supermassive black hole that draws gas to the center and ejects jets of matter seen in radio waves. This discovery from NASA’s X-ray Chandra Telescope and the Gemini International Telescope could push the limits of the speed at which astronomers expect galaxies to grow in the early universe.

Credit: X-ray: NASA/CXC/Univ. of Turin/V. Missaglia et al.; Optician: NASA/ESA/STScI and Gemini/NOIRLab/NSF/AURA International Observatory; Infrared: NASA/ESA/STScI; Radio: NRAO/AUI/NSF

In many ways, the 3C 297 has the mass of a galaxy cluster, a huge structure containing hundreds or even thousands of individual galaxies. Chandra X-ray data reveal large amounts of gas heated to millions of degrees, a distinguishing characteristic of a galaxy cluster. Astronomers also found a jet from the quasar that was 'bent' by interacting with its surroundings. Finally, Chandra’s data shows evidence that the other quasar jet collided with the surrounding gas, creating a "hot spot" of X-rays. These are typically characteristic of a cluster of galaxies. However, Gemini data indicates that there is only one galaxy in 3C 297. The nineteen galaxies that appear close to 3C 297 in one image are actually at very different distances.

In this new composite image, the Chandra data is in violet, the VLA data is in red and the Gemini data is in green. Visible light and infrared data from the Hubble Space Telescope (blue and orange respectively) were also included. One possibility for what happened to the vanished galaxies is that the gravitational pull of the larger galaxy, combined with the interactions between them, caused the 'fall' of the companion galaxies and assimilation by the main. Scientists believe that 3C 297 is most likely a "group of fossils" rather than a cluster of galaxies, a stage in galactic evolution where one galaxy is approaching and merging with others. If so, 3C 297 is the farthest fossil cluster ever found. More research and observations will shed light on the mystery.

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