One of the dishes of the Giant Metrowave Radio Telescope (GMRT) near Pune, Maharashtra, India.Credit: National Center for Radio Astrophysics
Exploring galaxies far from Earth may now be within reach.
How do stars form in distant galaxies? Astronomers have long attempted to answer this question by detecting radio signals emitted by nearby galaxies. But these signals weaken as the galaxy moves away from Earth, making it difficult for modern radio telescopes to receive them.
Now researchers in Montreal and India are picking up radio signals at a specific wavelength known as the 21 cm line from the most distant galaxy so far, giving astronomers a peek into the secrets of the early universe. This is the first time a radio signal of this kind has been detected from such a distance with the help of India’s giant Metrewave radio telescope.
A diagram showing the detection of a signal from a distant galaxy. Credit: Swadha Pardesi
“Galaxies emit many different kinds of radio signals. Until now, we could only pick up this particular signal from nearby galaxies, so our knowledge was limited to galaxies closer to Earth.” said Arnab Chakraborty, a postdoctoral fellow at McGill University under the supervision of Professor Matt Dobbs.
“But thanks to a naturally occurring phenomenon called gravitational lensing, we can capture faint signals from record-breaking distances, which can help us understand the composition of galaxies far from Earth. I will,” he adds.
Travel back in time to the early universe
For the first time, the research team was able to detect a signal and measure its gas composition from a distant star-forming galaxy known as SDSSJ0826+5630. The researchers observed that the atomic mass of this particular galaxy’s gas content is nearly twice the mass of the stars we see.
An image of radio signals from the galaxy. Credit: Chakraborty & Roy/NCRA-TIFR/GMRT
The signal detected by the team was emitted from this galaxy when the universe was just 4.9 billion years old, giving researchers a glimpse into the secrets of the early universe. “It’s his 8.8 billion year retrospective,” says Chakraborty, who studies cosmology at McGill University’s Physics Department.
pick up signals from distant galaxies
“Gravitational lensing magnifies signals coming from distant objects to help peer into the early universe. It is bent by the presence of another galaxy, which effectively magnifies the signal by a factor of 30, allowing it to be picked up by a telescope,” said co-assistant professor of physics at the Indian Institute of Science. Author Nirupam Roy says:
According to the researchers, these results point to the possibility of observing distant galaxies in a situation similar to gravitational lensing. It also opens exciting new opportunities to explore the cosmic evolution of stars and galaxies using existing low-frequency radio telescopes.
See: “Detection of HI 21 cm emission from a strongly lensed galaxy at z ∼ 1.3”, 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. This research was funded by McGill University and the Indian Institute of Science.
