It is now within reach to explore galaxies at far greater distances from Earth.
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 as the galaxy moves farther from Earth, making it difficult for current radio telescopes to pick them up.
Researchers in Montreal and India have now picked up a radio signal from the farthest galaxy yet at a specific wavelength known as the 21-cm line, allowing astronomers to delve deeper into the mysteries of the primordial universe. With the help of the giant Metrewave radio telescope in India, this is the first time that this type of radio signal has been detected at such a great distance.
Illustration showing the detection of a signal from a distant galaxy. 1 credit
“The galaxy emits different types of radio signals. Until now, it was only possible to pick up this particular signal from a nearby galaxy, which limits our knowledge of galaxies closest to Earth,” says Arnab Chakraborty, a postdoctoral researcher at McGill University under the direction of Professor Matt Dobbs.
He adds: “But with the help of a natural phenomenon called gravitational lensing, we can pick up a faint signal at a record distance. This will help us understand the formation of galaxies at much greater distances from Earth.”
Back in time to the primordial universe
For the first time, researchers have been able to detect the signal from a distant star-forming galaxy known as SDSSJ0826+5630 and measure the composition of its gas. The researchers note that the atomic mass of the gaseous contents of this particular galaxy is roughly twice the mass of stars visible to us.
Image of a galactic radio signal. 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 a glimpse into the mysteries of the early universe. “This is equivalent to going back in time 8.8 billion years,” says Chakraborty, who studies cosmology in the Department of Physics at McGill.
Capture the signal from a distant galaxy
“Gravitational lensing amplifies the signal from a distant object to help us peer into the early universe. In this specific case, the signal is distorted by another massive object, another galaxy, between the target and the observer. This effectively amplifies 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 show the feasibility of observing distant galaxies in similar situations using gravitational lensing. It also opens exciting new opportunities for exploring the cosmic evolution of stars and galaxies with 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, December 23, 2022, Available here. Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093 / mnras / stac3696
The Giant Metrewave Radio Telescope is built and operated by NCRA-TIFR. The research was funded by McGill University and the Indian Institute of Science.
