Astronomers pick up the radio signal from a distant galaxy
Exploring galaxies at much greater distances from Earth may now be within reach.
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 the farther a galaxy is from Earth, making it difficult for today’s radio telescopes to pick them up.
Now researchers from Montreal and India have captured a radio signal from the most distant galaxy yet at a specific wavelength known as the 21 cm line, allowing astronomers to peer into the secrets of the early universe. Using the Giant Metrewave Radio Telescope in India, this is the first time this type of radio signal has been detected at such a great distance.
“A galaxy emits different kinds of radio signals. Until now, it was only possible to pick up this specific signal from a nearby galaxy, limiting our knowledge to the galaxies closer to Earth,” said Arnab Chakraborty, a postdoctoral researcher at McGill University under the supervision of Professor Matt Dobs.
“But with the help of a naturally occurring phenomenon called gravitational lensing, we can pick up 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.
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 its gas composition. The researchers saw that the atomic mass of the gas content of this particular galaxy is almost twice the mass of the stars visible to us.
The signal detected by the team was emitted from this galaxy when the universe was only 4.9 billion years old, giving the researchers a glimpse into the secrets of the early universe. “It’s the equivalent of looking back in time 8.8 billion years,” said Chakraborty, who studies cosmology in McGill’s Department of Physics.
Picking up the signal from a distant galaxy
“Gravity lensing magnifies the signal coming from a distant object to help us see into the early universe. In this particular case, the signal is deflected by the presence of another massive body, another galaxy, between the target and the observer This effectively results in a magnification of the signal by a factor of 30, allowing the telescope to pick it up,” said study 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 feasibility of observing distant galaxies in similar situations using gravitational lenses. It also opens up exciting new possibilities for investigating the cosmic evolution of stars and galaxies with existing low-frequency radio telescopes.
Reference: “Detection of HI 21 cm emission from a strong lensed galaxy at z ∼ 1.3” by Arnab Chakraborty and Nirupam Roy, December 23, 2022, Monthly communications from the Royal Astronomical Society.
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.
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