GMRT Radio Halo Survey in galaxy clusters at z = 0.2 - 0.4. II.The eBCS clusters and analysis of the complete sample - AstrophysicsReportar como inadecuado




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Abstract: We present the results of the GMRT cluster radio halo survey. The mainpurposes of our observational project are to measure which fraction of massivegalaxy clusters in the redshift range z=0.2-0.4 hosts a radio halo, and toconstrain the expectations of the particle re-acceleration model for theorigin of the non-thermal radio emission. We selected a complete sample of 50clusters in the X-ray band from the REFLEX 27 and the eBCS 23 catalogues.In this paper we present Giant Metrewave Radio Telescope GMRT observations at610 MHz for all clusters still lacking high sensitivity radio information, i.e.16 eBCS and 7 REFLEX clusters, thus completing the radio information for thewhole sample. The typical sensitivity in our images is in the range 1$\sigma\sim 35-100 \mu$Jy b$^{-1}$. We found a radio halo in A697, a diffuseperipheral source of unclear nature in A781, a core-halo source in Z7160, acandidate radio halo in A1682 and ``suspect- central emission in Z2661.Including the literature information, a total of 10 clusters in the sample hosta radio halo. A very important result of our work is that 25 out of the 34clusters observed with the GMRT do not host extended central emission at thesensitivity level of our observations, and for 20 of them firm upper limits tothe radio power of a giant radio halo were derived. The GMRT Radio Halo Surveyshows that radio halos are not common, and our findings on the fraction ofgiant radio halos in massive clusters are consistent with the statisticalexpectations based on the re-acceleration model. Our results favour primary tosecondary electron models.



Autor: T. Venturi, S. Giacintucci, D. Dallacasa, R. Cassano, G. Brunetti, S. Bardelli, G. Setti

Fuente: https://arxiv.org/







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