E-Paper
GMRT catches rare cosmic tango of radio galaxies
The discovery of GMRT catching rare cosmic tango of radio galaxies was made by an international team led by Indian radio astronomers
A rare cosmic spectacle – two galaxies performing a tango (dance) – has been discovered by an international team led by Indian radio astronomers. The discovery was made recently using the upgraded Giant Metrewave Radio Telescope (GMRT) located near Khodad village about 80 km north of Pune. This front-ranking radio telescope was built and is being operated as an international facility by the National Centre for Radio Astrophysics (NCRA), Pune, of the Tata Institute of Fundamental Research (TIFR).
The discovery has been reported in the May 17, 2022 issue of leading international journal, Monthly Notices of the Royal Astronomical Society (Letters), published by the Oxford University Press. The team of researchers comprises professors Gopal Krishna (CEBS, Mumbai); Ravi Joshi (IIA, Bengaluru); Dusmanta Patra (SNBSCBS, Kolkata); X. Yang (SHAO, Shanghai); LC Ho (KIAA, Beijing); PJ Wiita (TCNJ, Ewing); and A Omar (ARIES, Nainital).
Over the active lifespan of a galaxy - which can last for tens of millions of years - the two relativistic jets grow out to millions of light-years on opposite sides. Usually, these jets of relativistic electrons/positrons, also carrying a magnetic field, are detected by radio telescopes as they intensely radiate radio waves by a mechanism called ‘synchrotron’. The first pair of twin radio objects, famously called the Twin-Radio-Galaxy (TRG) 3C 75, was discovered by American radio astronomers in 1985 using the Very Large Array (VLA) radio telescope located in New Mexico (USA). The discovery of a second TRG was reported in 1991, by a team of European and American radio astronomers, again using the VLA. The discovery of a third TRG, named J104454+354055, has come this year after a gap of three decades, through the use of the GMRT by the team in question led by Indian radio astronomers.
“The fact that this third such system has been discovered after a gap of three decades is testament to the extreme rarity of the phenomenon of TRGs. In this case too, the two bright elliptical galaxies are orbiting around their gravitational centre, along with their pairs of relativistic jets. The consequent wiggling of both jet pairs presents a rare spectacle of a ‘cosmic tango’ (see the figure attached). These radio jets are seen to extend over at least 1.5 million light-years. Further study of this rare object is in progress,” said professor Gopal Krishna.
“From this, we can expect to learn how these gigantic jets of relativistic plasma respond to the orbital motion of their parent galaxies and how they maintain their identity despite their side-way collisions. Compared to both its predecessors found three to four decades ago, this newly-discovered, third TRG is much better suited for quantitative modelling. This is because of its morphological purity, as it is apparently not encountering any environmental crosswind which would have distorted its jets,” the professor added.
