RSS chief pays tribute to Gauri Lankesh, Dharam Singh

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.

Jan 28: Hindu temple processions with an elephant adorned in ornaments carrying the idol, with percussionists and devotees walking side by side, are no new sight in Kerala. However, a similar procession in Kerala's cultural capital, Thrissur, turned heads. Hundreds of Muslims were seen holding hands and clearing traffic to help the procession move smoothly.

Muslims made way for the passage of a Hindu temple procession during their protest against Citizenship Amendment Act(ACT) in Thrissur on Saturday, January 25.

Various Muslim organisations had organised a mass protest in the Swaraj ground in the town. On the same day, the local Bhaktapriyam temple's procession was also taking place. Stuck in a dilemma, the temple authorities approached the police and the Muslim organisations to find a solution. The Muslim organisations then promised to help proceed the temple procession without any obstacles.

Nearly a thousand people who had turned up for the protest volunteered to clear traffic and control the crowd so that the temple procession could smoothly pass through the town.

A video of the procession was shared on Facebook by the Thrissur City Police on Saturday, which showed Muslims holding hands on either side of the procession to make way.

"Humanity is bigger than religion. That's the lesson the residents of Thrissur are giving to the country. Thrissur is truly the cultural capital of Kerala," read the caption of the post in Malayalam. The video soon went viral and was viewed by over 36k views.