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Leiden, Jul 2: Astronomers have discovered a luminous galaxy caught in the act of reionizing its surrounding gas only 800 million years after the Big Bang.

The research, led by Romain Meyer, PhD student at UCL in London, UK, has been presented at the virtual annual meeting of the European Astronomical Society (EAS).

Studying the first galaxies that formed 13 billion years ago is essential to understanding our cosmic origins. One of the current hot topics in extragalactic astronomy is 'cosmic reionization,' the process in which the intergalactic gas was ionized (atoms stripped of their electrons).

Cosmic reionization is similar to an unsolved murder: We have clear evidence for it, but who did it, how and when? We now have strong evidence that hydrogen reionization was completed about 13 billion years ago, in the first billion years of the universe, with bubbles of ionized gas slowly growing and overlapping.

The objects capable of creating such ionized hydrogen bubbles have however remained mysterious until now: the discovery of a luminous galaxy in which 60-100 percent of ionizing photons escape, is likely responsible for ionizing its local bubble. This suggests the case is closer to being solved.

The two main suspects for cosmic reionization are usually 1) a population of numerous faint galaxies leaking ~10 percent of their energetic photons, and 2) an 'oligarchy' of luminous galaxies with a much larger percentage (>50 percent) of photons escaping each galaxy.

In either case, these first galaxies were very different from those today: galaxies in the local universe are very inefficient leakers, with only <2-3 percent of ionizing photons escaping their host. To understand which galaxies governed cosmic reionization, astronomers must measure the so-called escape fractions of galaxies in the reionization era.

The detection of light from excited hydrogen atoms (the so-called Lyman-alpha line) can be used to infer the fraction of escaping photons. On the one hand, such detections are rare because reionization-era galaxies are surrounded by neutral gas which absorbs that signature hydrogen emission.

On the other hand, if this hydrogen signal is detected it represents a 'smoking gun' for a large ionized bubble, meaning we have caught a galaxy reionizing its surroundings. The size of the bubble and the galaxy's luminosity determines whether it is solely responsible for creating this ionized bubble or if unseen accomplices are necessary.

The discovery of a luminous galaxy 800 million years after the Big Bang supports the scenario where an 'oligarchy' of bright leakers emits most of the ionizing photons.

"It is the first time we can point to an object responsible for creating an ionized bubble, without the need for a contribution from unseen galaxies.

Additional observations with the upcoming James Webb Space Telescope will enable us to study further what is likely one of the best suspects for the unsolved case of cosmic reionization," said Meyer.

Chennai, Jun 22: Commuting the death sentence to life imprisonment for five convicts, the Madras High Court on Monday set free Chinnasamy, the main convict, who had also been sentenced to death in the Udumalpet Shankar honour killing case.

A Division Bench comprising Justice M. Sathyanarayanan and Justice M. Nirmal Kumar also dismissed the appeal by the state police against the acquittal of three persons by a lower court.

The Bench ordered the five convicts sentenced for life to undergo a jail term of not less than 25 years.

In 2016, V. Shankar, who had married C. Kausalya, was killed by a gang in Udumalpet in Tamil Nadu. The gang also injured Kausalya in the attack.

It was alleged the parents of Kausalya -- Chinnasamy, Annalakshmi -- were against the marriage.

P. Pandidurai, the uncle of Kausalya at the behest of Chinnasamy and Annalakshmi had hired a gang to kill Shankar.

The gang killed Shankar in broad daylight in a public place and Kausalya too got injured in the attack as she tried to save her husband.

The Principal District and Sessions Court in Tiruppur had convicted and sentenced to death six accused persons -- Chinnasamy, P. Jagadeesan, P. Selvakumar, M. Manikandan, M. Mathan alias Michael and P. Kalaithamilvaanan.

The court also sentenced two other accused, K. Dhanraj for life and Manikandan to a five year jail term, while acquitting Annalakshmi, Pandidurai and Prasanna.

The convicts had filed an appeal against their sentence in the Madras High Court while the police filed an appeal against the acquittal of three persons.