How are stars born in distant galaxies? Astronomers have long tried to answer this question by picking up radio signals from nearby galaxies. However, the farther the galaxy is from Earth, the weaker these signals become, making detection difficult for modern radio telescopes. One of the antennas of the giant Metrewave radio telescope near Pune in the state of Maharashtra in India.
Photo: National Center for Radio Astrophysics
But recently, researchers from Montreal and India picked up a radio signal with a wavelength called the 21-cm line, coming from the most distant galaxy known to date. Astronomers have thus been able to explore the mysteries of the beginnings of the universe. Thanks to the giant Metrewave radio telescope in India, we’ve been able to pick up these types of radio signals from such a distance for the first time.
“A galaxy emits different types of radio signals. So far, we have only been able to pick up this signal when it came from a neighboring galaxy, which limits our knowledge to galaxies close to Earth,” explains Arnab Chakraborty, a postdoctoral fellow at McGill University supervised by Professor Matt Dobbs.
“But thanks to a natural phenomenon called gravitational lensing, we were able to pick up a faint signal at a record distance. This will allow us to understand the composition of galaxies located very far from Earth,” he adds.
A window to the beginnings of the universe
For the first time, researchers have managed to receive a signal from a star-forming galaxy called SDSSJ0826+5630 and measure its gas composition. Researchers have found that the atomic mass of the gases in this galaxy is almost twice the mass of the stars we see.
The signal received by the team was emitted by this galaxy when the universe was just 4.9 billion years old, giving researchers a glimpse into the beginnings of the universe. “It’s like going back in time to 8.8 billion years ago,” says Arnab Chakraborty, who studies cosmology in McGill University’s Department of Physics and the McGill Trottier Space Institute.
A crucial amplification effect “Gravitational lensing amplifies the signal coming from distant objects, allowing us to observe the universe at its beginnings. In the case that concerns us, the signal is distorted by the presence of another massive body, the is called another galaxy that is between the target and the observer. The signal is thereby amplified by a factor of 30 and the telescope can pick it up,” explains Nirupam Roy, co-author of the study and associate professor in the Department of Physics, Indian Science Institute.
According to the researchers, these results show that, thanks to gravitational lensing, it is possible to observe distant galaxies in similar situations. They also open exciting possibilities to study the cosmic evolution of stars and galaxies with existing low-frequency radio telescopes.
The publication “Detection of HI 21 cm emission from a strong lensed galaxy at z ∼ 1.3” by Arnab Chakraborty and Nirupam Roy was published in Monthly Notices of the Royal Astronomical Society.
The giant Metrewave radio telescope was built and is operated by the Tata Institute for Basic Research’s National Center for Radio Astrophysics. This study was funded by McGill University and the Indian Institute of Science.