Radio multifrequency observations of the galaxy cluster pair Abell 399 − 401 with WSRT
| Autor: | C D Nunhokee, G Bernardi, S Manti, F Govoni, A Bonafede, T Venturi, D Dallacasa, M Murgia, R F Pizzo, O M Smirnov, V Vacca |
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| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Monthly Notices of the Royal Astronomical Society. 522:4421-4429 |
| ISSN: | 1365-2966 0035-8711 |
| DOI: | 10.1093/mnras/stad1158 |
| Popis: | Galaxy clusters are assembled via merging of smaller structures, in a process that generates shocks and turbulence in the intra cluster medium and produces radio diffuse emission in the form of halos and relics. The cluster pair A 399–A 401 represents a special case: both clusters host a radio halo. Recent Low Frequency Array (LOFAR) observations at 140 MHz revealed the presence of a radio bridge connecting the two clusters along with two relic candidates. These relics include one South of A 399 and the other in between the two clusters, in proximity of a shock front detected in X-ray observations. In this paper we present observations of the A 399–A 401 cluster pair at 1.7, 1.4, 1.2 GHz, and 346 MHz from the Westerbork Synthesis Radio Telescope (WSRT). We detect the radio halo in the A 399 cluster at 346 MHz, extending up to ∼650 kpc and with a 125 ± 6 mJy flux density. Its spectral index between 140 MHz and 346 MHz is α = 1.75 ± 0.14. The two candidate relics are also seen at 346 MHz and we determine their spectral indices to be α = 1.10 ± 0.14 and α = 1.46 ± 0.14. The low surface brightness bridge connecting the two clusters is below the noise level at 346 MHz therefore we constrain the bridge average spectral index to be steep, i.e. α > 1.5 at 95 per cent confidence level. This result favours the scenario where dynamically-induced turbulence is a viable mechanism to reaccelerate a population of mildly relativistic particles and amplify magnetic fields on scales of a few Mpcs. |
| Databáze: | OpenAIRE |
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