Astronomers from McGill College in Canada and the Indian Institute of Science (IISc) in Bengaluru have used information from the Large 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 date 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 gasoline from the encompassing medium of a galaxy falls onto the galaxy, the gasoline cools and varieties atomic hydrogen, which then turns into molecular hydrogen, and ultimately results in the formation of stars. Subsequently, understanding the evolution of galaxies over cosmic time requires tracing the evolution of impartial gasoline at completely different cosmological epochs.
Atomic hydrogen emits radio waves of 21 cm wavelength, which may 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 almost not possible to detect the emission from a distant galaxy utilizing present telescopes on account of 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 item’s location and motion; a higher worth of z signifies a farther object.)
Utilizing GMRT information, 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.
“Because of the 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 group 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 potential by a phenomenon known as gravitational lensing, by which the sunshine emitted by the supply is bent as a result of presence of one other huge physique, akin to 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 by the excessive redshift universe,” explains Roy.
The group additionally noticed that the atomic hydrogen mass of this specific galaxy is nearly twice as excessive as its stellar mass. These outcomes exhibit the feasibility of observing atomic gasoline from galaxies at cosmological distances in related lensed methods with a modest quantity of observing time. It additionally opens up thrilling new potentialities for probing the cosmic evolution of impartial gasoline with present and upcoming low-frequency radio telescopes within the close to future.
Yashwant Gupta, heart director at NCRA, mentioned, “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 may be confirmed and improved upon sooner or later.”
Extra data:
Arnab Chakraborty et al, Detection of H i 21 cm emission from a strongly lensed galaxy at z ∼ 1.3, Month-to-month Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac3696
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Report-breaking detection of radio sign from atomic hydrogen in extraordinarily distant galaxy (2023, January 16)
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