IIA researchers find evidence of interaction between a radio jet and interstellar gas

The Department of Science and Technology said this finding challenges the hypothesis that only large and massive galaxy jets which regulate star formation host AGN powered by massive black holes. Representational file image.
| Photo Credit: Reuters

Researchers from the Indian Institute of Astrophysics (IIA) have found evidence of an interaction between a radio jet emitted from a special kind of galaxy called Active Galactic Nuclei (AGN) and the surrounding interstellar medium. This interaction has been detected for the first time in a dwarf galaxy situated at a distance of about 14 million light years.

A radio jet is material that is spewed from the centre of some galaxies almost at the speed of light and sends out strong radio waves.

The Department of Science and Technology said this finding challenges the hypothesis that only large and massive galaxy jets which regulate star formation host AGN powered by massive black holes.

IIA researchers, combining data from radio to X-ray wavebands from the galaxy NGC 4395, observed evidence for such an interaction at the scale of 10 parsecs, or about 30 light years, around the black hole at the centre of this galaxy.

“We decided to investigate how the radio jet from a small black hole interacts with the gas in a dwarf galaxy called NGC 4395”, said Payel Nandi, the lead author and a PhD student at IIA (registered under the Joint Astronomy Programme of IISc).

“We used data from multiple ground and space-based telescopes such as Chandra for X-ray data, Gemini-North and Hubble Space Telescope for optical data, Gemini-North for infrared observations, ALMA for submillimeter observations, and the Very Large Array for radio observations,” she added.

Data from UVIT

They also used data from the UltraViolet Imaging Telescope (UVIT) on board AstroSat, India’s first dedicated space observatory and were able to discover a unique radio structure resembling a bipolar jet, whose core was centred at the black hole location. “This jet is relatively weak, but our multi-wavelength analysis of this 30-light year region showed that the jet is interacting with the surrounding gas, and possibly causing shock waves to propagate through it,” said C. S. Stalin at IIA, a co-author of the study.

“This study is important because of the discovery of jet-ISM interaction at very small spatial scales hitherto unknown,” added Mr. Stalin.