Rare hydrogen gas ring found in distant galaxy with no new stars by Pune astronomers

Astronomers at the Indian National Centre for Radio Astrophysics (NCRA) in Pune have found a galaxy with a large ring of hydrogen wrapped around it, but no stars.

Galaxies comprise of gas, solar systems, cosmic dust and stars. The galaxy observed by the researchers, AGC 203001, is located 260 million light-years away from Earth and shows no signs of star formation at all. This feature was peculiar to astrophysicists considering what is a well-know and widely-accepted model of galaxies and hydrogen rings — a prominent ring of hydrogen gas means more star formation is actively taking place in it.

Moreover, the ring is massive — about four times as wide as the Milky Way galaxy, making this starless hydrogen ring only the second of its kind observed in the universe (apart from the huge Leo Ring found in 1983), as per a study in the Monthly Notices of the Royal Astronomical Society . Looking at AGC 203001’s large ring in the visible light spectrum astronomers found no readings of stars or starlight from the ring.

Another feature scientists noted was the off-center position of the ring with regard to the galaxy. While researchers thought this happens by collision with an ‘intruder’ galaxy, but still results in large amounts of star formation in the resulting hydrogen rings, which wasn’t what they noticed with the ring discussed in this paper. Wadadekar said nearly 10 hours of observation were carried out using the GMRT in December 2017 while the astronomers observed the same galaxy for two hours with the Hawaii telescope in March 2019.

“A collision between two galaxies leads to such an off-center ring with stars in it. But this was not found in our discovery,” lead author of the study, lead author of the study Omkar Bait explained, adding, “We now plan to carry out surveys and study radio emissions of nine similar galaxies that have been shortlisted with similar criteria.”

Using the Pune-based Giant Meterwave Radio Telescope (GMRT) and the Canada-France-Hawaii Telescope (CFHT) at Mauna Kea in Hawaii, Indian astronomers along with their collaborators in France (CNRS scientists) not only found how the hydrogen was spread across the galaxy.

The team of astronomers set out to use the high-sensitivity, high-resolution imaging offered by the Giant Metrewave Radio Telescope (GMRT) in Pune and the Canada-France-Hawaii-Telescope (CFHT) in Hawaii. There isn’t any clear explanation for why AGC 203001 is starless with a massive hydrogen ring. But scientists intend to take notes and compare AGC 203001 to many other hydrogen gas-rich galaxies where no new stars form.