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Astronomers Detect Radio Signal from Strongly Gravitationally Lensed Galaxy

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Using archival data from the Giant Metrewave Radio Telescope, astronomers have captured a radio signal at a specific wavelength known as the 21 cm line from SDSS J0826+5630, a star-forming galaxy that existed nearly 9 billion years ago. This is the first time this type of radio signal has been detected at such a large distance.

The radio image of SDSS J0826+5630. Image credit: Chakraborty & Roy, doi: 10.1093/mnras/stac3696.

“A galaxy emits different kinds of radio signals,” said Dr. Arnab Chakraborty, a postdoctoral researcher at McGill University.

“Until now, it’s only been possible to capture this particular signal from a galaxy nearby, limiting our knowledge to those galaxies closer to Earth.”

“But thanks to the help of a naturally occurring phenomenon called gravitational lensing, we can capture a faint signal from a record-breaking distance.”

“This will help us understand the composition of galaxies at much greater distances from Earth.”

Using archival data from the Giant Metrewave Radio Telescope in India, Dr. Chakraborty and his colleague, Dr. Nirupam Roy from the Indian Institute of Science, detected the signal from a distant star-forming galaxy known as SDSS J0826+5630 and measured its gas composition.

They observed the atomic mass of the gas content of this particular galaxy is almost twice the mass of the stars visible to us.

The radio signal was emitted from this galaxy when the Universe was only 4.9 billion years old, enabling the astronomers to glimpse into the secrets of the early Universe.

“It’s the equivalent to a look-back in time of 8.8 billion years,” Dr. Chakraborty said.

“Gravitational lensing magnifies the signal coming from a distant object to help us peer into the early Universe,” Dr. Roy added.

“In this specific case, the signal is bent by the presence of another massive body, another galaxy, between the target and the observer.”

“This effectively results in the magnification of the signal by a factor of 30, allowing the telescope to pick it up.”

The team’s results demonstrate the feasibility of observing faraway galaxies in similar situations with gravitational lensing.

“It also opens exciting new opportunities for probing the cosmic evolution of stars and galaxies with existing low-frequency radio telescopes,” the authors said.

Their paper was published in the Monthly Notices of the Royal Astronomical Society.

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Arnab Chakraborty & Nirupam Roy. 2023. Detection of H i 21 cm emission from a strongly lensed galaxy at z ~ 1.3. MNRAS 519 (3): 4074-4081; doi: 10.1093/mnras/stac3696

Source : Breaking Science News

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