Radio haloes in Sunyaev–Zel'dovich-selected clusters of galaxies: the making of a halo?

Abstract

Radio halos are synchrotron radio sources detected in some massive galaxy clusters. Their Mpc-size indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio halos and to understand their connection with cluster-cluster mergers and with the thermal component of the intra-cluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive clusters in a wider redshift range. With the aim of discovering new radio halos and understanding their connection with cluster-cluster mergers, we have selected from the Planck Early source catalog the most massive clusters, and we have observed with the Giant Metrewave Radio Telescope at 323 MHz those objects for which deep observations were not available. We have discovered new peculiar radio emission in three of the observed clusters finding: (i) a radio halo in the cluster RXCJ0949.8+1708; (ii) extended emission in Abell 1443 that we classify as a radio halo plus a radio relic, with a bright filament embedded in the radio halo; (iii) low-power radio emission is found in CIZA J1938.3+5409 which is ten times below the radio -X-ray correlation, and represents the first direct detection of the radio emission in the "upper-limit" region of the radio -X-ray diagram. We discuss the properties of these new radio halos in the framework of theoretical models for the radio emission.

New giant radio sources and underluminous radio halos in two galaxy clusters

“…9), similarly to other few clusters reported in the literature Sommer et al 2017;Bonafede et al 2015). That region of the P 1.4GHz − M 500 diagram is usually occupied either by upper limits or by ultra steep spectrum radio halos, however, A1451 and Z0634 do not seem to host radio halos with steep spectra (Sect.…”

Mpc-scale diffuse radio emission in two massive cool-core clusters of galaxies

“…Next, two rounds of direction-dependent calibration (peeling), ionospheric modeling (Intema et al 2009) and wide-field imaging were performed. At this point, all sources beyond a radius of 10 arcmin from the primary beam center were removed (e.g., Bonafede et al 2015), thus creating a data set suitable for final imaging in CASA.…”

Clusters of Galaxies and the Cosmic Web with Square Kilometre Array

“…The first system of radio halo and relic was discovered in a massive new Planck cluster by and were followed by discoveries in other clusters (e.g. Giacintucci et al, 2013;Bonafede et al, 2015). These newly discovered clusters have flatter entropy profiles at the cores and are more likely to be disturbed given the fact that these were missed in the X-ray flux limited catalogues due to their more disturbed morphology.…”

“…Apart from X-ray flux-limited samples of galaxy clusters that have been explored so far, with the telescopes such as the Planck, the South Pole Telescope and the Atacama Cosmology Telescope that detect clusters using the Sunyaev-Ze'ldovich effect, mass limited samples can now be explored. Radio surveys of complete mass limited samples are ongoing and will provide results in the coming years (Basu, 2012;Cuciti et al, 2015;Bonafede et al, 2015).…”

“…The statistical occurrence of the diffuse radio sources is critical to study their origin and evolution in the context of the evolution of the clusters themselves. Current telescopes have allowed a limited number of statistical studies owing to the long observations needed to image with high sensitivity (Venturi et al, , 2008Kale et al, 2013Kale et al, , 2015Cuciti et al, 2015;Bonafede et al, 2015).…”