Record-breaking detection of radio signal from atomic hydrogen in extremely distant galaxy

Astronomers from McGill College in Canada and the Indian Institute of Science (IISc) in Bengaluru have used knowledge from the Big Meterwave 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 biggest to this point by a big margin. That is additionally the primary confirmed detection of robust lensing of 21 cm emission from a galaxy. The findings have been revealed within the Month-to-month Notices of the Royal Astronomical Society.

Atomic hydrogen is the essential gas required for star formation in a galaxy. When scorching ionized fuel from the encircling medium of a galaxy falls onto the galaxy, the fuel cools and types atomic hydrogen, which then turns into molecular hydrogen, and finally results in the formation of stars. Subsequently, understanding the evolution of galaxies over cosmic time requires tracing the evolution of impartial fuel at completely different cosmological epochs.

Atomic hydrogen emits radio waves of 21 cm wavelength, which could be detected utilizing low frequency radio telescopes just like the GMRT. Thus, 21 cm emission is a direct tracer of the atomic fuel content material in each close by and distant galaxies. Nevertheless, this radio sign is extraordinarily weak and it’s practically unattainable to detect the emission from a distant galaxy utilizing present telescopes attributable to their restricted sensitivity.

Till now, essentially 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.)

Utilizing GMRT knowledge, Arnab Chakraborty, postdoctoral 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 signal 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 traveled from the supply to the telescope,” says Chakraborty. The sign detected by the crew was emitted from this galaxy when the universe was solely 4.9 billion years previous; in different phrases, the look-back time for this supply is 8.8 billion years.

This detection was made doable by a phenomenon referred to as gravitational lensing, during which the sunshine emitted by the supply is bent as a result of presence of one other large physique, resembling an early kind 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 few issue of 30, permitting us to see via the excessive redshift universe,” explains Roy.

The crew additionally noticed that the atomic hydrogen mass of this explicit galaxy is sort of twice as excessive as its stellar mass. These outcomes show the feasibility of observing atomic fuel from galaxies at cosmological distances in related lensed techniques with a modest quantity of observing time. It additionally opens up thrilling new prospects for probing the cosmic evolution of impartial fuel with present and upcoming low-frequency radio telescopes within the close to future.

Yashwant Gupta, heart director at NCRA, stated, “Detecting impartial hydrogen in emission from the distant Universe is extraordinarily difficult and has been one of many key science objectives of GMRT. We’re pleased with this new path breaking end result with the GMRT, and hope that the identical could be confirmed and improved upon sooner or later.”