• Detecting massive young star-forming complexes beyond the visible boundary of faraway dwarf galaxies using the Ultraviolet Imaging Telescope on AstroSat.
• The discovery was made by an international team of astronomers from India, the USA and France, led by Dr. Kanak Saha, Professor of Astronomy, at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune and was published in Nature.
• The discovery is an important part of a Ph.D. thesis of a research scholar, Mr. Anshuman Borgohain, the lead author of the article, from Tezpur University, Assam.
• This is also a success story of the Associateship programme for faculty and students of Indian Universities run by IUCAA, Pune on behalf of the University Grants Commission, Ministry of Education.

Giant radio galaxies are the largest single astrophysical objects in the Universe with sizes of over a few million light years. These gigantic objects are often larger than about 30 Milky Way-sized galaxies placed in a single line. Their huge sizes are due to collimated jets of highly energetic particles squirting out from supermassive black holes of about a billion solar masses or more residing in the centres of these radio-loud active galaxies. IUCAA scientists have been studying this class of objects which pose a number of challenging astrophysical questions over many years. They have reported the discovery of hundreds of giant radio sources from deep surveys at radio wavelengths accounting for a major fraction of all such sources known.

In their recent work, an international team including IUCAA scientists have reported an enigmatic barbell-shaped giant radio galaxy J223301+131502 from observations with the Giant Metrewave Radio Telescope (GMRT) in India and the Low-Frequency Array (LOFAR) in Europe at radio wavelengths and with the William Herschel Telescope in the Canary Islands, Spain, at optical wavelengths. This giant radio galaxy is about 6 million light-years across and exhibits a number of interesting features including a prominent kink and twist in the jets and diffuse relic lobes. The observed features in the jets are possibly due to a combination of the development of plasma instabilities and the precession of the central supermassive black hole. Dr. Pratik Dabhade, formerly at IUCAA and now at the Instituto de Astrofísica de Canarias, who led this project said that ‘we initially noticed the peculiar morphology in a unique environment. However, only after sensitive observations with GMRT and LOFAR, its exceptionally long, collimated, and powerful jets were unveiled’.

‘The diffuse relic lobes with the radio jets reaching its inner edges suggest that the jet activity from the supermassive black hole could be episodic, which has many interesting astrophysical implications’ opined Professor Dhruba J Saikia from IUCAA. This giant radio galaxy is about 200 million years old and resides in a cluster of galaxies. Professor Somak Raychaudhury, Director, IUCAA highlighted that ‘this source provides an opportunity of studying the interaction of the jets with the external cluster environment from deep observations at x-ray wavelengths’. The team has been granted time to observe the source with the highly competitive Chandra X-ray Observatory. Professor Huub Rottgering from Leiden Observatory, the Netherlands, summarised to say that ‘these fascinating observations show that the long life of this radio galaxy was full of events: big obstacles had to be overcome for the source to be able to grow to a size about sixty times larger than our Galaxy’.

Contacts:

	Prof. Somak Raychaudhury (IUCAA, India) E-mail: somak_at_iucaa.in Phone: +91-20-25604231
	Prof. Dhruba J Saikia (IUCAA, India) E-mail: dhrubasaikia_at_iucaa.in
	Dr. Pratik Dabhade (LERMA, France) E-mail: pratikdabhade13_at_gmail.com
	Dr. Rupjyoti Gogoi (Tezpur University, India)
	Prof. Francoise Combes (Observatoire de Paris, France)
	Prof. Shyam N. Tandon (IUCAA, India)

* please change _at_ to @

Team members: