Image Credit: X-ray: NASA/CXC/Univ. of Torino/V. Missaglia et al.; Optical: NASA/ESA/STScI & International Gemini Observatory/NOIRLab/NSF/AURA; Infrared: NASA/ESA/STScI; Radio: NRAO/AUI/NSF
This image shows a galaxy called 3C 297 that is lonelier than expected after it likely attracted and absorbed its former companion galaxies. The lone galaxy is about 9.2 billion light-years from Earth and contains a quasar, a supermassive black hole that draws gas from the center of the galaxy and generates powerful jets of matter seen in radio waves. This result from NASA’s Chandra X-ray Observatory and the Gemini International Observatory may push the limits of how fast astronomers expect galaxies to grow in the early universe.
In many respects, 3C 297 has the qualities of a galaxy cluster, a gigantic structure containing hundreds or even thousands of individual galaxies. X-ray data from Chandra reveal large amounts of gas heated to millions of degrees, a distinctive feature of a galaxy cluster. The astronomers also found a jet from the quasar, seen by the Karl G. Jansky Very Large Array, that has bent as it interacted with its surroundings. Finally, the Chandra data shows evidence that the other quasar jet has slammed into the surrounding gas, creating an X-ray “hotspot.” These are typical features of a galaxy cluster. However, data from the Gemini Observatory show that there is only one galaxy in 3C 297. The nineteen galaxies that appear near 3C 297 in a Gemini image are actually at very different distances.
In this new composite image, Chandra data is purple, VLA data is red, and Gemini data is green. Visible light and infrared data from the Hubble Space Telescope (blue and orange respectively) have also been included. The lone galaxy (3C 297) and the position of its supermassive black are identified in a labeled version of the image, along with the black hole jets, X-ray hotspot, and hot gas. The field of view in this image is too small to show any of the 19 galaxies that are not at the same distance as 3C 297.
One theory for what happened to the vanished galaxies is that the gravitational pull of the larger galaxy, combined with the interactions between them, caused the companion galaxies to fall off and be assimilated by alpha. The team believes that 3C 297 is likely a “fossil group” rather than a galaxy cluster, a stage of galactic evolution in which one galaxy approaches and merges with others. If that’s the case, 3C 297 represents the most distant fossil group ever found.
The authors cannot rule out the presence of dwarf galaxies around 3C 297, but their presence still would not explain the lack of larger galaxies like the Milky Way. Nearby examples are M87 in the Virgo Cluster, which has had large galactic companions for billions of years. However, 3C 297 will spend billions of years essentially alone.