Astronomers from McGill College in Canada and the Indian Institute of Science (IISc) in Bengaluru have used knowledge from the Large Metrewave Radio Telescope (GMRT) in Pune to detect a radio sign originating from atomic hydrogen in a particularly distant galaxy.
“The astronomical distance over which such a sign has been picked up is the most important to this point by a big margin. That is additionally the primary confirmed detection of robust lensing of 21 cm emission from a galaxy”, in response to an IISc assertion. The findings have been printed in ‘Month-to-month Notices of the Royal Astronomical Society.’
Atomic hydrogen is the fundamental gasoline required for star formation in a galaxy. When sizzling ionised gasoline from the encircling medium of a galaxy falls onto the galaxy, the gasoline cools and kinds atomic hydrogen, which then turns into molecular hydrogen, and ultimately results in the formation of stars, it was defined.
“Due to this fact, understanding the evolution of galaxies over cosmic time requires tracing the evolution of impartial gasoline at completely different cosmological epochs”, the assertion stated. Atomic hydrogen emits radio waves of 21 cm wavelength, which might be detected utilizing low frequency radio telescopes just like the GMRT. Thus, 21 cm emission is a direct tracer of the atomic gasoline content material in each close by and distant galaxies.
Nonetheless, this radio sign is extraordinarily weak and it’s practically unattainable to detect the emission from a distant galaxy utilizing present telescopes resulting from their restricted sensitivity. “Till now, probably the most distant galaxy detected utilizing 21 cm emission was at redshift z=0.376, which corresponds to a look-back time – the time elapsed between detecting the sign and its unique emission – of 4.1 billion years (Redshift represents the change in wavelength of the sign relying on the thing’s location and motion; a better worth of z signifies a farther object),” it stated.
Utilizing GMRT knowledge, Arnab Chakraborty, post-doctoral researcher on the Division of Physics and Trottier House Institute of McGill College, and Nirupam Roy, Affiliate Professor, Division of Physics, IISc, have detected a radio sign from atomic hydrogen in a distant galaxy at redshift z=1.29.
“As a result of immense distance to the galaxy, the 21 cm emission line had redshifted to 48 cm by the point the sign travelled from the supply to the telescope,” says Chakraborty. The sign detected by the workforce was emitted from this galaxy when the universe was solely 4.9 billion years outdated; in different phrases, the look-back time for this supply is 8.8 billion years.
This detection was made attainable by a phenomenon referred to as gravitational lensing, by which the sunshine emitted by the supply is bent as a result of presence of one other huge physique, equivalent to an early sort elliptical galaxy, between the goal galaxy and the observer, successfully ensuing within the “magnification” of the sign. “On this particular case, the magnification of the sign was a couple of issue of 30, permitting us to see by way of the excessive redshift universe,” explains Roy.
The workforce additionally noticed that the atomic hydrogen mass of this explicit galaxy is nearly twice as excessive as its stellar mass. These outcomes display the feasibility of observing atomic gasoline from galaxies at cosmological distances in comparable lensed programs with a modest quantity of observing time. It additionally opens up thrilling new prospects for probing the cosmic evolution of impartial gasoline with present and upcoming low-frequency radio telescopes within the close to future, the assertion stated.
Yashwant Gupta, Centre Director at NCRA (Nationwide Centre for Radio Astrophysics), stated, “Detecting impartial hydrogen in emission from the distant Universe is extraordinarily difficult and has been one of many key science targets of GMRT. We’re proud of this new path-breaking end result with the GMRT, and hope that the identical might be confirmed and improved upon sooner or later.”