![]() "In this specific case, the magnification of the signal was about a factor of 30, allowing us to see through the high redshift universe," explains Roy. This detection was made possible by a phenomenon called gravitational lensing, 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 resulting in the "magnification" of the signal. The signal detected by the team was emitted from this galaxy when the universe was only 4.9 billion years old in other words, the look-back time for this source is 8.8 billion years. "Due to the immense distance to the galaxy, the 21 cm emission line had redshifted to 48 cm by the time the signal travelled from the source to the telescope," says Chakraborty. Using GMRT data, Arnab Chakraborty, a post-doctoral researcher at the Department of Physics and Trottier Space Institute of McGill University, and Nirupam Roy, Associate Professor, the Department of Physics, IISc, have detected a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29. "Until now, the most distant galaxy detected using 21 cm emission was at redshift z=0.376, which corresponds to a look-back time - the time elapsed between detecting the signal and its original emission - of 4.1 billion years (Redshift represents the change in wavelength of the signal depending on the object's location and movement a greater value of z indicates a farther object)," it said. However, this radio signal is extremely weak and it is nearly impossible to detect the emission from a distant galaxy using current telescopes due to their limited sensitivity. Thus, 21 cm emission is a direct tracer of the atomic gas content in both nearby and distant galaxies, the PTI report said. ![]() ![]() "Therefore, understanding the evolution of galaxies over cosmic time requires tracing the evolution of neutral gas at different cosmological epochs", the statement said.Ītomic hydrogen emits radio waves of 21 cm wavelength, which can be detected using low-frequency radio telescopes like the GMRT. When hot ionised gas from the surrounding medium of a galaxy falls onto the galaxy, the gas cools and forms atomic hydrogen, which then becomes molecular hydrogen, and eventually leads to the formation of stars, it was explained. The findings have been published in Monthly Notices of the Royal Astronomical Society.Ītomic hydrogen is the basic fuel required for star formation in a galaxy.
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