INDIA: According to sources, researchers have recorded radio signals from a galaxy almost 9 billion light-years from Earth.
It has never been possible to receive a signal from this far away.
The signals were picked up by a special wavelength called the “21-centimeter line” or “hydrogen line,” which is thought to be given off by neutral hydrogen atoms.
“By a wide margin, the astronomical distance across which such a signal has been detected is the biggest yet. Furthermore, this is the first independently verified discovery of significant lensing of a galaxy’s 21-cm emission,” according to an IISc statement.
The results have been published in Monthly Notices of the Royal Astronomical Society.
In a galaxy, atomic hydrogen is the fundamental fuel needed for star creation. It was explained that as hot, ionized gas from a galaxy’s surrounding medium falls onto the galaxy, the gas cools and transforms into atomic hydrogen, molecular hydrogen, and stars.
The sentence says, “Therefore, to understand how galaxies have changed over cosmic time, we must look at how neutral gas has changed at different cosmological epochs.”
Low-frequency radio telescopes like the Giant Metrewave Radio Telescope (GMRT) can detect radio waves with a wavelength of 21 cm that is emitted by atomic hydrogen.
The report stated that this makes 21-cm emission a direct tracer of the atomic gas concentration in both adjacent and far-off galaxies.
However, this radio signal is quite feeble, making it practically difficult for modern telescopes to detect the emission from a far-off galaxy.
“The farthest galaxy discovered by 21 cm emission up to this point was at a redshift of z=0.376, or a look-back time of 4.1 billion years (redshift represents the change in wavelength of the signal depending on the location and motion of the object; a greater value of z indicates a farther object),” it said.
Arnab Chakraborty, a post-doctoral researcher at the Trottier Space Institute and the Department of Physics at McGill University, and Nirupam Roy, an associate professor in the Department of Physics at the Indian Institute of Science, have discovered a radio signal from atomic hydrogen in a far-off galaxy at redshift z = 1.29.
The signal from the source to the telescope redshifted the 21 cm emission line to 48 cm because of the great distance to the galaxy, claims Chakraborty.
In other words, the look-back time for this source is 8.8 billion years because the signal that the scientists discovered was produced by this galaxy when the universe was just 4.9 billion years old.
This discovery was made possible by a phenomenon called gravitational lensing. In this case, the light from the source is bent because there is another huge body, like an early-type elliptical galaxy, between the target galaxy and the observer, which “magnifies” the signal.
Roy notes that in this particular instance, the signal was magnified by around a factor of 30, which allowed scientists to see through the high redshift universe.
The scientists also noted that the galaxy in question has an atomic hydrogen mass that is nearly twice as great as its stellar mass.
These results show that, given a reasonable amount of time to look, it is possible to see atomic gas from galaxies far away in similar lensed systems, as long as there is enough time to look.
The press release also opens up exciting new ways to study the development of neutral gas in the universe with low-frequency radio telescopes in the near future.
Director of the NCRA (National Center for Radio Astrophysics), Yashwant Gupta, stated, “One of the main scientific objectives of GMRT has been neutral hydrogen detection, which is a very difficult task. With this new, ground-breaking result from the GMRT, we are pleased and hopeful that it can be validated and enhanced in the future.”