Astronomers Have Received a Radio Signal from a Distant Galaxy

Giant Metrewave Radio Telescope
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Giant Metwave Radio Telescope

One of the dishes from the Giant Meterwave Radio Telescope (GMRT) near Pune, Maharashtra, India. Credit: National Center for Radio Astrophysics

Exploring galaxies at greater distances from Earth may now be within reach.

How do stars form in distant galaxies? Astronomers have been trying to answer this question for a long time by detecting radio signals emitted by nearby galaxies. However, as the galaxy moves away from Earth, these signals weaken, making it difficult for existing radio telescopes to receive.

Now researchers from Montreal and India have captured a radio signal at a specific wavelength known as the 21cm line from the most distant galaxy ever, giving astronomers a glimpse into the mysteries of the early universe. This is the first time that this type of radio signal has been detected at such a great distance, with the help of the Giant Metwave Radio Telescope in India.

Detecting Signals from a Distant Galaxy

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

“The galaxy emits different types of radio signals. Until now, it has only been possible to capture this particular signal from a nearby galaxy, limiting our knowledge to galaxies closer to Earth,” says Arnab Chakraborty, a postdoctoral researcher at McGill University under the supervision of Professor Matt Dobbs.

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

A glimpse back into the early universe

For the first time, researchers have been able to detect a signal from a distant star-forming galaxy known as SDSSJ0826+5630 and measure its gas composition. The researchers observed that the gas composition of this particular galaxy is almost twice the atomic mass of the stars we see.

A Radio Signal from a Galaxy Far Away

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

The signal detected by the team emanated from this galaxy when the universe was only 4.9 billion years old, giving researchers a glimpse into the secrets of the early universe. “This is equivalent to looking back 8.8 billion years,” says Chakraborty, who studies cosmology in McGill’s Department of Physics.

Picking up a signal from a galaxy far, far away

“Gravitational lensing magnifies the signal from a distant object to help us glimpse the early universe. In this particular case, the signal is distorted by the presence of another massive object, another galaxy, between the target and the observer. This effectively results in a 30-fold magnification of the signal, allowing the telescope to pick it up,” says co-author Nirupam Roy, an associate professor in the Department of Physics at the Indian Institute of Science.

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

Reference: “Detection of HI 21 cm emission from a strongly lensed galaxy at Z ~ 1.3” by Arnab Chakraborty and Nirupam Roy, 23 Dec 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 the Indian Institute of Science.

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