Astronomers Use Giant Galaxy Clusters As A Lens To Study Distant Radio Galaxy

Radio telescopes are essentially massive and extremely sensitive radio receivers that can scan the heavens for extremely faint radio emissions coming from objects in the most distant parts of the universe. A team of astronomers recently used the National Science Foundation's Karl G. Jansky Very Large Array (VLA) to take advantage of naturally occurring phenomena to detect a distant galaxy believed to be the faintest radio-emitting object ever found. The team used distant clusters of galaxies as a natural lens to study objects even further away.

Astronomers say the galaxy clusters were used as gravitational lenses. A gravitational lens is when the gravitational pull of galaxies in the cluster bends and magnifies light and radio waves coming from objects that are further away. A VLA radio image was superimposed on a visible-light image taken by the Hubble Space Telescope in the composite image above. Astronomers note that in the image, the large visible red-orange objects are radio relics. Large structures were possibly caused by shockwaves inside the foreground cluster known as MACSJ0717.5+3745.

MACSJ0717.5+3745 is more than 5 billion light-years from Earth. Detailed VLA observations show that many galaxies in the image are emitting radio waves in addition to visible light. Data revealed the galaxy shown in the enlargement box is more than 8 billion light-years distant. Its light and radio waves are bent by the gravitational lensing effect of the galaxy cluster in front of it.

The more distant galaxy is called VLAHFF-J071736.66+374506.4, and it has been magnified more than six times by the gravitational lens, which is what allowed the VLA to be able to detect it. Researcher Ian Haywood from Oxford University says that VLAHFF-J071736.66+374506.4 is probably the faintest radio-emitting object ever detected. The galaxy is 300 times less massive than the Milky Way and is seen as it was at a time when the universe was less than half its current age. Researchers say that the observations give valuable insights into star formation and low mass galaxies at that time and how they eventually assembled into more massive galaxies.