Radio observations shed extra mild on the properties of Pandora’s Cluster

Utilizing the Very Massive Array (VLA), astronomers have carried out radio observations of a galaxy cluster Abell 2744, nicknamed Pandora’s Cluster. Because of this, they obtained the deepest high-resolution radio picture of this cluster, which gives extra insights into its properties. The new findings had been revealed June 25 on the arXiv pre-print server.

Galaxy clusters comprise as much as 1000’s of galaxies and are the most important constructions within the universe which are self-bound by their very own gravity. Observations present that galaxy clusters usually kind because of mergers and develop by accreting sub-clusters.

Abell 2744 is an enormous X-ray galaxy cluster situated some 4 billion mild years away from the Earth. The cluster has a virial mass of about 740 trillion photo voltaic lots and showcases a robust central halo, together with an prolonged tail.

Pandora’s Cluster has been a goal of a number of observational packages at a number of radio and millimeter wavelengths with totally different angular resolutions and sensitivities, reaching a decision of three.5 by 3.5 arcseconds with a sensitivity of roughly 100 mJy/beam.

Now, a crew of astronomers led by Esteban A. Orozco of the Nationwide Autonomous College of Mexico, stories that they managed to acquire a greater high quality radio picture of this cluster.

“With an rms [root-mean-square] noise of ≈ 1 µJy/beam, on the part heart, and sub-arcsec angular decision (θ_1/2 = 0′′.82), that is the deepest and most detailed radio picture of Abell 2744 ever obtained,” the researchers wrote within the paper.

The observations detected 93 radio sources in Pandora’s Cluster, out of which 46 have optical or near-infrared counterparts. The overwhelming majority of them (88) seem like point-like sources, whereas 5 of them turned out to be prolonged or multi-component sources.

Based on the paper, the recognized sources are galaxies with a median efficient radius of 6,550 mild years and stellar lots spanning from 660,000 to 160 billion photo voltaic lots. The median star formation price for these galaxies was discovered to be roughly 1.9 photo voltaic lots per yr, whereas the median flux density was measured to be 15.6 µJy/beam.

Furthermore, the astronomers detected 9 energetic galactic nuclei (AGN) candidates within the cluster. They calculated that the AGN fraction for the Pandora’s Cluster is at a stage of 10–20%, which is per the worth of 14% derived from simulations and fashions.

The examine discovered that the Pandora’s Cluster higher restrict to the radio luminosity at 6.0 GHz is 4.1 duodecillion erg/s. The astronomers estimate that the cluster has a radio spectral index of roughly 0.7.

The authors of the paper have additionally carried out a seek for radio counterparts of the so-called “little purple dots” (LRD) galaxies as a part of the examine. Typically, LRDs are compact galaxies with purple optical colours and even broad hydrogen-alpha emission traces, suggesting the presence of sort I AGNs. Nonetheless, the researchers discovered no radio counterparts of those galaxies within the VLA information.

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