Uncovering the Secrets of the Early Universe: Astronomers Capture Radio Signals From a Distant Galaxy

They are now able to probe galaxies much greater distances away from Earth.

How do stars form in distant galaxies? Astronomers have long been trying 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 current radio telescopes to pick them up.

Now researchers from Montreal and India have captured a radio signal from the most distant galaxy down to a precise 21 cm line, allowing astronomers to peer into the secrets of the early universe. With the help of the Giant Metrewave Radio Telescope in India, this is the first radio signal of its kind to be detected at such a great distance.

Illustration showing the detection of a signal from a distant galaxy. Credit: Swadha Pardesi

“The galaxy emits different types of radio signals.” Until now, only this signal could be picked up from a nearby galaxy, limiting our knowledge to these galaxies closer to Earth,” says Arnab Chakraborty, Post-Doctoral Researcher at McGill University under Professor Matt Dobbs.

“But with the help of a naturally occurring phenomenon called gravitational lensing, we can capture a faint signal from a record-breaking distance. This will help us understand the composition of galaxies at much greater distances from Earth,” he adds.

We must look back in time to the ancient universe

First, the researchers were able to detect a signal from a distant star-forming galaxy known as SDSSJ0826+5630 and measure the composition of the gas. The researchers observed that the atomic mass of the gas of this particular galaxy is almost twice the mass of the stars visible to us.

Image of a radio signal from a galaxy. Credit: Chakraborty & Roy/NCRA-TIFR/GMRT

The team detected a signal emitted from this galaxy when the universe was only 4.9 billion years old, allowing researchers to peer into the secrets of the early universe. “It’s the equivalent of a time mirror of 8.8 billion years,” says Chakraborty, who studies cosmology at McGill’s Department of Physics.

Pick up a signal from a distant galaxy

“A gravitational lens magnifies the signal coming from a distant object to help us see the universe. In this specific case, the signal is deflected by the presence of another massive body, another galaxy, between the target and the point of view. This effectively results in a magnification of the signal by a factor of 30 allowing the telescope to pick it up,” says co-author Nirupam Roy, Associate Professor in the Department of Physics at the Indian Institute of Science.

According to the researchers, these results demonstrate the possibility of keeping distant galaxies in similar situations with gravitational lensing. It also opens up exciting new opportunities for studying the cosmic evolution of stars and galaxies with existing low-frequency radio telescopes.

Report: “Detection of III 21 cm emission from a highly stable galaxy at z 1.3” by Arnab Chakraborty and Nirupam Roy, 23 December 2022; Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3696

The Giant Metrewave Radio Telescope was built and operated by NCRA-TIFR. The research was funded by McGill University and conducted at the Indian Institute of Science.