In a new discovery, astronomers from the Indian Institute of Astrophysics (IIA) and their collaborators have found a new ultra-diffuse galaxy forming 430 million light years from Earth in the constellation Leo.
This nascent galaxy is located at the tip of the longest tidal tail ever discovered, stretching out from galaxy NGC 3785. The ground-breaking find offers new insights into galaxy evolution and formation.
The tidal tail, a long stream of stars and interstellar gas, was formed by the gravitational interaction between NGC 3785 and a neighbouring galaxy.
Measuring an unprecedented 1.27 million light years in length, this tidal tail is not only the longest known to date, but it also holds clues to the formation of ultra-diffuse galaxies (UDGs), which have very low surface brightness and are challenging to detect.
The Discovery and its Significance
The discovery was first made by Omkar Bait, now at SKA, U.K., while he was a student at the National Centre for Radio Astrophysics (NCRA) in Pune. Bait recognized the uniqueness of the tidal tail and shared his observations with NCRA’s Dr. Yogesh Wadadekar and IIA’s Dr. Sudhanshu Barway.
Together with Chandan Watts, a Ph.D. student at IIA and the lead author of the study, they embarked on a detailed investigation of the phenomenon.
Using advanced image processing techniques, Watts conducted a precise photometric analysis of the tidal tail and confirmed its extraordinary length. “We found that this extraordinary tidal tail stretches for 1.27 million light years, making it the longest tidal tail discovered so far,” Watts said.
What makes this discovery even more significant is the presence of a nascent ultra-diffuse galaxy at the tip of the tidal tail. “This particular tail’s extraordinary length and the presence of star-forming clumps along its span make it a unique case for understanding how faint and diffuse galaxies come into existence,” explained Dr. Barway, co-author of the study.
Implications for Galaxy Formation
The formation of the ultra-diffuse galaxy is likely driven by the gravitational interaction between NGC 3785 and a neighboring galaxy.
This discovery offers a rare opportunity to observe the creation of new, faint structures in the universe and provides crucial insights into the formation of ultra-diffuse galaxies, which have long been a subject of fascination for astronomers.
“The tidal tail offers a glimpse into how galaxies like ultra-diffuse ones, with very low surface brightness, come into being,” Watts added, noting that such features are often missed by traditional surveys due to their faintness.
Future Prospects
The discovery paves the way for future studies on low surface brightness features, which can offer more insights into galaxy evolution.
Newly launched missions like the Euclid Space Telescope and upcoming ground-based surveys, such as the Rubin Observatory’s Legacy Survey of Space and Time (LSST), are expected to uncover more such faint tidal features, thanks to their enhanced sensitivity.
The research, which has been published in the November issue of Astronomy & Astrophysics Letters, is authored by Chandan Watts from IIA and Pondicherry University, Dr. Sudhanshu Barway from IIA, Dr. Omkar Bait from SKA, U.K., and Dr. Yogesh Wadadekar from NCRA, Pune.
This discovery marks a significant milestone in the study of galaxy interactions and the formation of faint, diffuse structures in the universe.