Using the powerful Magellan Telescopes in Chile, a team of Italian astronomers has turned their gaze toward the enigmatic giant galaxy cluster known as Abell 2744, affectionately dubbed the Pandora's Cluster. Their findings, detailed in a paper published on February 13 via the preprint server arXiv, offer fresh insights into the intricate properties of this cosmic behemoth.
Galaxy clusters, vast collections of up to thousands of galaxies bound together by the force of gravity, present unparalleled opportunities for studying galaxy evolution and cosmology. Formed through the gradual accumulation of mass and the merging of smaller structures, these clusters represent the largest gravitationally bound entities in the universe.
Situated approximately 4 billion light years away from Earth, the Pandora's Cluster looms as a colossal assembly of galaxies, estimated to possess a mass roughly 4 trillion times greater than that of the sun. Its origins trace back to a tumultuous series of mergers, with at least four smaller galaxy clusters converging over a span of 350 million years.
Previous observations have unveiled the complex nature of the Pandora's Cluster, showcasing a remarkable confluence of galactic activity evident in both radio and X-ray data. Captivated by its celestial spectacle, a team of astronomers spearheaded by Davide Abriola from the University of Milan embarked on an investigative journey, leveraging MegaCam—a sophisticated mosaic CCD camera mounted on one of the Magellan Telescopes.
In their latest study, the researchers present an enhanced weak lensing analysis of Abell 2744, harnessing deep Magellan/MegaCam multiband imaging data spanning a vast field of view. Employing cutting-edge software tools such as mccd and ngmix for PSF reconstruction and shape measurement, the team meticulously dissected the intricate dynamics of the cluster.
Their findings revealed a staggering projected total mass of approximately 2.56 quadrillion solar masses, concentrated within a radius of 7.66 million light years from the brightest cluster galaxy in the south-west region. This places the Pandora's Cluster among the most massive galaxy clusters documented to date.
Further analysis uncovered the presence of three distinct high-density peaks within the inner core of the cluster, indicative of ongoing merger activity. Notably, one peak, exhibiting significantly higher density and a signal-to-noise ratio of 14.0, was situated in close proximity to the brightest cluster galaxy in the south-eastern quadrant, while the remaining two peaks were identified in the north-western corner.
The authors assert that these observations underscore the dynamic nature of the cluster, affirming its status as a site of intense merger activity—a conclusion reinforced by a comparative analysis with high-precision strong lensing data from the James Webb Space Telescope.