One of the dishes of the Giant Meterwave Radio Telescope (GMRT) near Pune, Maharashtra, India. Credit: National Center for Radio Astrophysics
Searching for galaxies at far greater distances from Earth can now be close.
How do stars form in distant galaxies? Astronomers have long tried to answer this question by detecting the radio signals emitted by nearby galaxies. However, these signals weaken as a galaxy moves away from Earth, making it difficult for current radio telescopes to receive.
Now researchers from Montreal and India have captured a radio signal of a specific wavelength, known as the 21cm line, from the farthest galaxy ever, allowing astronomers to probe the secrets of the early universe. With the help of the Giant Meterwave Radio Telescope in India, this is the first time such a radio signal has been detected at such a great distance.
Image showing the detection of a signal from a distant galaxy. Credit: Swadha Pardesi
“A galaxy emits different kinds of radio signals. Until now, it was only possible to capture this particular signal from a nearby galaxy, and we’ve limited our knowledge to galaxies closer to Earth,” said Arnab Chakraborty, a Postdoctoral Fellow under Professor Matt Dobbs at McGill University. says.
“But with the help of a naturally occurring phenomenon called gravitational lensing, we are able to capture a weak signal at a record-breaking distance. This will help us understand the composition of galaxies at much greater distances from Earth,” he adds.
A look back in time to the early universe
For the first time, the researchers were able to detect the signal from a distant star-forming galaxy known as SDSSJ0826+5630 and measure the gas composition. The researchers observed that the atomic mass of this particular galaxy’s gas content is nearly twice the mass of stars we can see.
Image of a radio signal from the galaxy. Credits: Chakraborty & Roy/NCRA-TIFR/GMRT
The signal detected by the team was released from this galaxy when the universe was only 4.9 billion years old, allowing researchers to peek into the secrets of the early universe. “This is equivalent to looking into the past 8.8 billion years,” says Chakraborty, who studies cosmology in McGill’s Department of Physics.
Receiving a signal from a distant galaxy
“Gravitational lensing helps us look into the early universe by magnifying the signal from a distant object. In this particular case, the signal is bent by the presence of another large object, another galaxy, between the target and the observer. This effectively results in a 30x magnification of the signal, and the telescope can’t find it.” allows it to get it,” 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 feasibility of observing distant galaxies in situations similar to gravitational lensing. It also offers exciting new opportunities to investigate 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 Meterwave Radio Telescope is built and operated by NCRA-TIFR. The research was funded by McGill University and the Indian Institute of Science.
