A Deep uGMRT view of the ultra steep spectrum radio halo in Abell 521
| Autor: | Santra, Ramananda, Kale, Ruta, Giacintucci, Simona, Markevitch, Maxim, Luca, Federico De., Bourdin, Herve, Venturi, Tiziana, Dallacasa, Daniele, Cassano, Rossella, Brunetti, Gianfranco, Buch, Kaushal |
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| Rok vydání: | 2023 |
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| Druh dokumentu: | Working Paper |
| Popis: | We present the first detailed analysis of the ultra-steep spectrum radio halo in the merging galaxy cluster Abell 521, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations. The combination of radio observations (300-850 MHz) and archival X-ray data provide a new window into the complex physics occurring in this system. When compared to all previous analyses, our sensitive radio images detected the centrally located radio halo emission to a greater extent of $\sim$ 1.3 Mpc. A faint extension of the southeastern radio relic has been discovered. We detected another relic, recently discovered by MeerKAT, and coincident with a possible shock front in the X-rays, at the northwest position of the center. We find that the integrated spectrum of the radio halo is well-fitted with a spectral index of $-1.86 \pm 0.12$. A spatially resolved spectral index map revealed the spectral index fluctuations, as well as an outward radial steepening of the average spectral index. The radio and X-ray surface brightness are well correlated for the entire and different sub-parts of the halo, with sub-linear correlation slopes (0.50$-$0.65). We also found a mild anti-correlation between the spectral index and X-ray surface brightness. Newly detected extensions of the SE relic and the counter relic are consistent with the merger in the plane of the sky. Comment: 31 pages (total), 35 figures, 7 tables, 2 appendix (12 figures, 2 tables). Accepted for publication in Astrophysical Journal (APJ) |
| Databáze: | arXiv |
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