Indian researchers discover faint galaxy 136 light years away
Researchers from India, in collaboration with those from France, have discovered a faint star-forming galaxy around 136 light years away, using the Ultraviolet Imaging Telescope (UVIT) on-board India’s only space observatory Astrosat.
The galaxy, which the researchers have named UVIT J2022, remained undetected because it lay in front of a much brighter galaxy that is further away. Previously, it was thought that UVIT J2022 was an interacting galaxy because of the superimposition of the background and the foreground.
As optical telescopes get more powerful, researchers are able to detect more of such extremely faint galaxies — those with lower surface brightness than the surrounding sky. Such faint galaxies are thought to account for up to 15% of the mass of the universe, but researchers are still looking for them.
The researchers first got a hint that it might be a separate entity while studying the galaxy NGC 6902A in the background using the Dark Energy Camera Legacy Survey (DECaLS) colour image that showed excess Far Ultraviolet (FUV).
Far Ultraviolet is usually found in the star-forming regions of the galaxy and is emitted by two types of massive and short-lived young stars. When the researchers investigated further, they found that the star-forming region they had detected using FUV was 136 million light-years away whereas the background galaxy NGC 6902A is at a distance of 825 million light-years, meaning they were two different galaxies.
The research was conducted by a team of researchers, including Jyoti Yadav, Mousumi Das and Sudhanshu Barway, from the Indian Institute of Astrophysics-Bangalore in collaboration with Francoise Combes of College de France, Chaire Galaxies et Cosmologie, Paris. Other than UVIT aboard AstroSat, the researchers used data from Multi-Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope (VLT) in Chile, Infra-Red Survey Facility (IRSF) in South Africa, and from Dark Energy Camera Legacy Survey (DECaLS).
The research was published in the journal ‘Astronomy & Astrophysics’.