doi:10.1038/nindia.2013.48 Published online 29 March 2013
Using a ground-based radio telescope, researchers have detected a new pair of giant fossil radio lobes in a famous radio galaxy one billion light years away from Earth1. The discovery demonstrates that this galaxy, called 3C452, had an earlier phase of activity that produced giant blobs of radio-emitting plasma extending over 3 million light years.
Such intense radio activity in 3C452 might have injected huge energy into the surrounding space, indicating the possible role of radio galaxies in shaping the evolution of the universe.
Radio galaxies emit radio waves with jets of high-energy particles from their central core. A supermassive black hole at the core of radio galaxies sets off such emissions, spreading them many millions of light years into intergalactic space. Given their strong contribution to cosmic evolution, it is essential to observe and analyse radio galaxies such as 3C452. Previous studies had identified that this galaxy has just one pair of radio lobes. However, those studies gave no clues to its past, including whether it had any active radio phase.
The researchers captured radio images of this galaxy using the Giant Metrewave Radio Telescope (GMRT) installed at a location near Pune. A special image analysis software revealed its new giant outer pair of radio lobes. These two peripheral radio lobes are clearly the relics of a previous episode of jet activity in this galaxy, as indicated by their faint radio emissions.
"The study suggests that even the most unsuspected radio galaxies might have undergone multiple episodes of jet activity from the supermassive black holes located in their cores. Active phases of galaxies may usually be much longer than the typical estimate of 10-100 million years," says Gopal Krishna, a co-author of the study.
The authors of this work are from: National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Pune, India and Department of Physics, The College of New Jersey, New Jersey, USA.