UKHRUL: An international research team of astronomers at the National Astronomical Observatory of Japan (NAOJ) lead by Ronaldo Laishram discovered a massive protocluster that existed 12.6 billion years ago and named it the Loktak Protocluster. This marks a significant development towards understanding how early dense environments shape galaxy growth over cosmic time.
Laishram is an observational astronomer working on galaxy evolution and large-scale structure. Currently at NAOJ he works with the James Webb Telescope, Hubble Space Telescope and Subaru Telescope. Laishram has also worked in multiple commendable projects in galaxy formation and evolution namely LAE Protocluster at z~5, Spiderweb Protocluster, COSMOS Overdensity and CAMIRA Clusters.
Galaxies in the present universe have gathered into groups forming enormous galaxy clusters containing hundreds or even thousands of galaxies. In the early Universe however, denser regions of matter grew under gravity and developed into galaxy clusters. These early forming structures are called protoclusters, the ‘seed’ of present-day galaxy clusters.
“Protoclusters are the construction sites of the most massive structures in the present-day Universe”, says Laishram. “Finding such a clealy organized system at this early epoch gives us a rare chance to study how environment affects galaxy growth in the young Universe,” he added on the Subaru Telescope website.
The Subaru Telescope, a large-infrared telescope was used to conduct a sky survey leading discovery of the Loktak protocluster. Young galaxies with active star-formation often emit a special type of light called Lyman-alpha emission and galaxies found through this signal are called Lyman-alpha emitters—useful for tracing structures in the early Universe.
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Using a special filter to detect this light, the team mapped a vast area of sky and identified a region where galaxies were strongly concentrated. The discovered structure was named after the Loktak Lake in Laishram’s home state. The reference reflects the manner in which four separate galaxy concentrations are linked together into one larger structure resembling the floating islands of the lake.
Galaxies in the Loktak Protocluster were compared with the galaxies in ordinary regions of the universe using different kinds of light from the James Webb telescope particularly Ultraviolet (UV) light and optical light. UV light highlights places where new stars are actively forming while optical light shows the distribution of older stars that already exist in the galaxy.
The study revealed an interesting detail, in UV light both galaxies looked about the same size which means the active-star forming regions near their centers were similar however in the optical light, galaxies in the protocluster were about 1.4 times larger signifying that those galaxies had more extended outer regions filled with older stars. Thus proving that the appearance of galaxies is shaped not only by what they are born with, but also by where they grow up—and that this process began in the earliest chapters of cosmic history.
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Congratulating Laishram’s success on X, Chief Minister Yumnam Khemchand stated, “Named after our iconic Loktak Lake, this landmark discovery places Manipur on the global scientific map and stands as a proud testament to the talent and execellence of our people. May this achievement inspire generations of young minds.”
The former Chief Minister N. Biren Singh also took on X stating, “This proud moment reflects the brilliance, dedication, and potential of our youth. By connecting the name of Loktak with the story of the Universe you have made every Manipur proud.”