Indian Astronomers Discover The Dying Remnants Of A Previously Unseen Giant Radio Galaxy

A giant radio galaxy dying nine billion light years away has been discovered by a team of astronomers of the National Centre for Radio Astrophysics (NCRA) here.

Budding scientist Prathamesh Tamhane, a former student of Indian Institute of Science Education and Research, Pune, led the project under the supervision of Yogesh Wadadekar at NCRA.

Wadadekar said, "When we see the sun, it is a mere eight light minutes away, while the discovered galaxy is nine billion light years away. We see it as it was nine billion years in the past. Compare this to the age of the universe, which is about 14 billion years old. So, the galaxy is seen by us today, as it was, when the universe was about one-third of its present age."

Astronomers claimed that such giant radio galaxies were extremely rare, especially in the distant universe. Spotting such a rare object in its short-lived dying phase is an absolutely unique phenomenon. Such galaxies harbour a super massive black hole at their centre.

Astronomers used the Giant Metrewave Radio Telescope (GMRT) for observing this galaxy, emitting powerful radio waves. It has an extent of a whopping 4 million light years. Hence, it is called a giant radio galaxy. These results have been published in the November issue of the international journal - Monthly Notices of the Royal Astronomical Society, London.

The team has used these observations to understand the properties of the magnetic field in the region between galaxies in the distant universe, a frontier area of research in astronomy. Wadadekar said, "This galaxy provides us with a unique space laboratory. We can gain a better understanding of its formation and evolution by carefully studying its properties."

While radio galaxies with size less than a million light years are common, giant radio galaxies are extremely rare, even more so at large cosmic distances. This galaxy, known by the scientific name "J021659-044920", is the newest member of this elite group.

Tamhane said, "What makes J021659-044920 special is that it has been caught in dying phase. Such dying radio objects are best studied using a low frequency radio telescope such as the GMRT."

For their analysis, the team combined their GMRT observations with previous observations made with a slew of international ground and space based telescope facilities - XMM-Newton Space Telescope in X-ray, the Japanese Subaru telescope in optical, UK's Infrared Telescope in near-infrared, Nasa's Spitzer Space Telescope in mid-infrared and the Jansky Very Large Array (USA) in high frequency radio bands. By using data from multiple telescopes spanning across the electromagnetic spectrum, they were able to carry out a comprehensive and incredibly detailed analysis of the physical conditions around this distant galaxy.