An extract from the analyzed field of view centered on the Pandora cluster observed with Magellan/MegaCam. Credit: Abriola et al., 2024.
Using the Magellan Telescopes in Chile, Italian astronomers observed a giant galaxy cluster known as Abell 2744, nicknamed the Pandora Cluster. Results of the observation campaign, presented in an article published on February 13 on the preprint server arXivprovide more information about the properties of this cluster.
Galaxy clusters contain up to thousands of galaxies held together by gravity. They form by mass accretion and infall of smaller substructures and are the largest gravitationally bound structures known in the universe. They could therefore constitute excellent laboratories for studying the evolution and cosmology of galaxies.
Located about 4 billion light years from Earth, the Pandora Cluster is a giant galaxy cluster, estimated to be about 4 trillion times more massive than the sun. This appears to be the result of a simultaneous stacking of at least four distinct, smaller galaxy clusters, occurring over a period of 350 million years.
Previous observations of Pandora’s Cluster have revealed that it exhibits one of the most complex merger phenomena ever detected, observed in both radio and X-ray data. The cluster has also attracted the attention of a team of astronomers led by Davide Abriola from the University of Milan in Italy, who decided to study it with MegaCam, a large mosaic CCD camera installed on one of the Magellan telescopes.
“In this paper, we present an enhanced WL (weak lens) analysis of the Abell 2744 galaxy cluster using Magellan/MegaCam deep multiband imaging data covering a field of view of approximately 31′ × 33′ …. For our study, we applied a pipeline based on two brand-new software packages, mccd and ngmix, for point spread function (PSF) reconstruction and shape measurement, respectively,” the researchers wrote in the paper.
First, the new observations revealed that the Pandora cluster has a total projected mass of about 2.56 quadrillion solar masses, less than 7.66 million light-years away from the galaxy cluster the brightest in the southwest. This makes it one of the most massive galaxy clusters discovered so far.
The reconstructed total mass distribution revealed the presence of three high-density peaks, substructures located at the heart of the Pandora cluster. One, with a higher density and a signal-to-noise ratio of 14.0, is in the southeastern part of the cluster, very close to the brightest galaxy cluster, while the other two are found in the northwest corner.
According to the authors of the article, these results confirm that the cluster is not relaxed but is undergoing a complex merger, as previous studies suggested. They added that this is also confirmed by a comparison with a new high-precision strong lensing analysis of the central region of the cluster, based on data from the James Webb Space Telescope (JWST).
More information:
Davide Abriola et al, An improved analysis of weak Magellanic lenses from the Abell 2744 galaxy cluster, arXiv (2024). DOI: 10.48550/arxiv.2402.08364
Journal information:
arXiv
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