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A research scholar from Tezpur University, Anshuman Borgohain, has discovered that new stars are forming beyond the visible boundaries of a sample of distant Blue Compact Dwarf (BCD) galaxies situated about 1.5 – 3.9 billion light-years away from earth.

“It is still unclear how dwarf galaxies of the past have evolved into the ones in the present day. Hence, capturing their assembly process over the cosmic ages is considered as one of the important links to complete the picture of galaxy formation and evolution,” Anshuman said.

Commending AstroSat/UVIT’s imaging capabilities he said, “It is opening up promising avenues in the field of extragalactic astronomy”.

Dr Gogoi, co-author and Assistant Professor of Physics at Tezpur University and associate at IUCAA said, “The current work is an inspiration to young researchers of the country as this utilizes data from India’s indigenous satellite, AstroSat. This also showcases the glorious association of IUCAA and a university, which surely will motivate the researchers working in Indian Universities. We look forward to enhancing this collaborative endeavour between IUCAA and Tezpur University”.

Prof Kanak Saha, co-author of the article and Professor of Astronomy at IUCAA, who conceived the study, emphasized that, “The resolving power of UVIT and UV deep field imaging techniques have indeed been the key to spotting these very young, faint and large star-forming clumps,” Saha said.

He mentioned that it would not have been possible to detect these faraway clumps at slightly larger distances from us and that we do not have such an example in present-day dwarf galaxies.

Dr Bruce Elmegreen, who contributed to the study, is a principal research staff in the IBM Research Division, USA, said, “It has been a mystery how some small galaxies like these can have such active star formation.”

Dr Elmegreen explained that these observations point to the funnelling of outer accreting gas further inwards due to gravitational forces exerted by massive outer clumps.

Anshuman Borgohain

“The discovery teaches us how surprisingly the star formation can proceed in relatively pristine low-metallicity gas”, said Prof. Francoise Combes of Observatoire de Paris, France, another co-author, and Professor at the College de France.

Prof Shyam Tandon, another co-author of this study and ex-emeritus Professor at IUCAA, has wondered whether these stellar clumps could have been sources of Lyman continuum photons, that ionise the neutral hydrogen gas.

This discovery forms a vital part of Anshuman’s PhD thesis.

Prof Vinod K. Jain, Vice-Chancellor of Tezpur University and Prof Somak Raychaudhury, Director of IUCAA expressed their delight over the discovery and the successful association of Tezpur University with IUCAA through the UGC’s visiting Associateship Programme at IUCAA.

Prof Jain said, “Understanding the birth and fate of the cosmos has been an ever-fascinating puzzle for humankind. The discovery of such unseen phenomena in these distant dwarf galaxies is just another piece of the puzzle and a glimpse of the unknown that new state-of-the-art observatories are starting to show and have to offer in near future.”

The discovery was a joint outcome of a study by an international team of astronomers from India, USA and France, conceived using the UltraViolet Imaging Telescope (UVIT) onboard AstroSat, India’s first dedicated multi-wavelength space observatory.

Working under the joint supervision of Dr Rupjyoti Gogoi at Tezpur University and Prof Kanak Saha at IUCAA, Borgohain was the lead author of a research article on the study that was published in renowned multidisciplinary science journal Nature on July 20.

The team is thankful and privileged to have such a state-of-the-art observational facility, developed and operated by the Indian Space Research Organization in collaboration with several Indian and foreign research laboratories, that led to this important discovery. Future endeavours to create such facilities would ensure the continuity of scientific excellence in India. Mr. Anshuman also expresses his gratitude to the DST-INSPIRE programme by the government of India that provides financial support for doctoral studies.