IISc and McGill University astronomers, using data from the Giant Metrewave Radio Telescope (GMRT) in Pune, have detected a radio signal originating from atomic hydrogen in a faraway galaxy.
According to IISc, the astronomical distance over which the signal has been picked up is the largest ever, and far by a huge margin.?
Even though it’s possible to detect radio waves with 21 centimetres of the wavelength emitted by atomic hydrogen using low-frequency radio telescopes such as the GMRT, the radio signals are extremely weak, making it almost impossible to detect emissions from a distant galaxy.
The most distant galaxy detected through this process so far was at redshift z=0.376. The value talks about the look-back time or the time elapsed between the detection and the original emission, which in this case was around 4.1 billion years.?
Astronomer Arnab Chakraborty, a postdoctoral researcher at the Department of Physics and Trottier Space Institute of McGill University, along with Nirupam Roy, associate professor, department of Physics, IISc, made use of data from GMRT to detect a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29.
As per the official IISc statement, the signal was emitted when the universe was just 4.9 billion years old -- a look back time of 8.8 billion years.
To the unaware, atomic hydrogen is formed when hot ionised gas from the surrounding medium of a galaxy drops onto it and cools. The change that turns it into molecular hydrogen leads to the formation of stars. Understanding the evolution of neutral gas thus becomes crucial in understanding the evolution of galaxies.
Researchers tracked the detection to a phenomenon dubbed gravitational lensing, which causes the light emitted by the source to bend due to the presence of another massive body, in a way similar to an early-type elliptical galaxy between the observer and the target galaxy, resulting in a magnified signal.
Roy explained, “In this specific case, the magnification of the signal was about a factor of 30, allowing us to see through the high redshift universe.”
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