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20th of June 2018
The MACS J0417-1554 cluster of galaxies
by Sandhu et al.
Clusters of galaxies are the most massive gravitationally bound objects in the universe. These clusters grow through collisions and mergers, which result in cluster-wide magnetic fields, generating radio halos via synchrotron radiation. Galaxy clusters can be bright X-ray sources, with the X-ray emission revealing the thermal component of the gas in the cluster. MACS J0417.5-1154, discovered in the Massive Cluster Survey, is a hot, massive cluster. It was initially detected at low radio frequencies, 235 MHz, 610 MHz, and 1575 MHz, prompting Sandhu et al. to extend these studies to higher frequencies with the Australia Telescope Compact Array. The image above shows a natural-weighted image of the entire region of the MACS J0417-1154 at 5.5 GHz, made with the inner five antennas in the H168 array configuration. The synthesized beam, 46 arcseconds by 32 arcseconds is shown in the bottom left-hand corner. Contours start at 5x the rms noise level of 8 μJy/beam. After removing the contributions from the bright point sources near the centre of the cluster, the diffuse emission can be measured. The level of diffuse emission at 5.5 and 9 GHz is consistent with an extrapolation from 610 MHz and 1575 MHz. The results are published in "The peculiar cluster MACS J0417.5-1154 in the C and X-bands" in Astrophysics and Space Science.

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