Exploring the galaxy at far greater distances from Earth is now within reach.
How do stars form in distant galaxies? Astronomers have long tried to answer this question by detecting radio signals emitted by nearby galaxies. However, these signals become weaker the farther the galaxy is from Earth, making it difficult for today’s radio telescopes to pick up on them.
Now researchers from Montreal and India have picked up radio signals from the most distant galaxies but at a specific wavelength known as the 21 cm band, allowing astronomers to dig deeper into the mysteries of the early universe. With the help of the Giant Metrewave radio telescope in India, this is the first time this type of radio signal has been detected at such a great distance.
The illustration shows the detection of a signal from a distant galaxy. Credit: Sawada Pardesi
“A galaxy emits different types of radio signals. Until now, this particular signal was only possible to be picked up from nearby galaxies, which limited our knowledge of the galaxies closest to Earth,” said Arnab Chakraborty, a postdoctoral researcher at McGill University. under Supervision by Professor Matt Dobbs.
But with the help of a natural phenomenon called gravitational lensing, we can pick up on faint signals from great distances. This will help us understand the formation of galaxies at much greater distances from Earth.”
Looking back in time to the early universe
For the first time, researchers were able to detect signals from a distant star-forming galaxy known as SDSSJ0826+5630 and measure the composition of its gas. The researchers noted that the atomic mass of the gas in this particular galaxy is nearly twice the mass of stars visible to us.
Image of radio signal from galaxy. Credit: Chakraborty and Roy/NCRA-TIFR/GMRT
The signal the team detected was emitted from this galaxy when the universe was only 4.9 billion years old, allowing researchers to glimpse the mysteries of the early universe. “This is the equivalent of looking back in time 8.8 billion years,” said Chakraborty, who studies cosmology in the Department of Physics at McGill University.
Catch signals from distant galaxies
“Gravitational lensing amplifies signals coming from distant objects to help us see into the early universe. In this particular case, the signal is deflected by the presence of another massive object, another galaxy, between the target and observer. This effectively amplifies the signal by a factor of 30, enabling telescopes to pick it up,” said co-author Nirupam Roy, professor in the Department of Physics at the Indian Institute of Science.
According to the researchers, these results demonstrate the feasibility of observing distant galaxies in similar situations using gravitational lensing. It also opens up exciting new opportunities to investigate the cosmic evolution of stars and galaxies using today’s low-frequency radio telescopes.
Reference: “21 cm HI emission detected from an intensely lensed galaxy at z∼1.3” by Arnab Chakraborty and Nirupam Roy, 23 Dec. 2022, Available here. Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3696
The Giant Metrewave Radio Telescope was built and operated by NCRA-TIFR. This research was funded by McGill University and the Indian Institute of Science.
