Astronomers detect radio signal from atomic hydrogen in distant galaxy

Astronomers from McGill University in Canada and the Indian Institute of Science (IISc) in Bengaluru have detected a radio signal originating from atomic hydrogen in an extremely distant galaxy using data from the Giant Metrewave Radio Telescope (GMRT) in Pune.

The signal was picked up over the greatest astronomical distance. This is also the first time that strong lensing of 21 cm emission from a galaxy has been confirmed.

The research was published in the Royal Astronomical Society’s Monthly Notices.

Arnab Chakraborty, a postdoctoral researcher at McGill University’s Department of Physics and Trottier Space Institute, and Nirupam Roy, Associate Professor at IISc’s Department of Physics, used GMRT data to detect a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29.

“Because of the enormous distance from the galaxy, the 21 cm emission line had redshifted to 48 cm by the time the signal arrived at the telescope,” Chakraborty explained.

The signal detected by the team was emitted from this galaxy when the universe was only 4.9 billion years old, giving this source an 8.8 billion-year look-back time.

This detection was made possible by gravitational lensing, a phenomenon in which the light emitted by the source is bent due to the presence of another massive body, such as an early type elliptical galaxy, between the target galaxy and the observer, effectively magnifying the signal.

“In this particular case, the signal magnification was approximately a factor of 30, allowing us to see through the high redshift universe,” Roy explained.