Radio footprints of a minor merger in the Shapley Supercluster: From supercluster down to galactic scales

Abstract

Context. The Shapley Supercluster (⟨z⟩≈0.048) contains several tens of gravitationally bound clusters and groups, making it an ideal subject for radio studies of cluster mergers. Aims. We used new high sensitivity radio observations to investigate the less energetic events of mass assembly in the Shapley Supercluster from supercluster down to galactic scales. Methods. We created total intensity images of the full region between A3558 and A3562, from ∼230 to ∼1650 MHz, using ASKAP, MeerKAT and the GMRT, with sensitivities ranging from ∼6 to ∼100 μJy beam−1. We performed a detailed morphological and spectral study of the extended emission features, complemented with ESO-VST optical imaging and X-ray data from XMM-Newton. Results. We report the first GHz frequency detection of extremely low brightness intercluster diffuse emission on a ∼1 Mpc scale connecting a cluster and a group, namely: A3562 and the group SC 1329–313. It is morphologically similar to the X-ray emission in the region. We also found (1) a radio tail generated by ram pressure stripping in the galaxy SOS 61086 in SC 1329–313; (2) a head-tail radio galaxy, whose tail is broken and culminates in a misaligned bar; (3) ultrasteep diffuse emission at the centre of A3558. Finally (4), we confirm the ultra-steep spectrum nature of the radio halo in A3562. Conclusions. Our study strongly supports the scenario of a flyby of SC 1329–313 north of A3562 into the supercluster core. This event perturbed the centre of A3562, leaving traces of this interaction in the form of turbulence between A3562 and SC 1329–313, at the origin of the radio bridge and eventually affecting the evolution of individual supercluster galaxies by triggering ram pressure stripping. Our work shows that minor mergers can be spectacular and have the potential to generate diffuse radio emission that carries important information on the formation of large-scale structures in the Universe.

The Coma Cluster at LOFAR Frequencies. II. The Halo, Relic, and a New Accretion Relic

“…At the center of the diffuse source region, there is a bright transverse bar. Such a bar has been detected in other bent tails (e.g., in A2443, Clarke et al 2013; and recently in the Shapley supercluster, Venturi et al 2022) and is predicted by simulations of interacting AGN tails and shocks (Nolting et al 2019). The length of this source, measured from the relic's edge down to the endpoints of the jets, is 10′, corresponding to 280 kpc at the Coma redshift.…”

Radio fossils, relics, and haloes in Abell 3266: cluster archaeology with ASKAP-EMU and the ATCA

“…However, new and highly sensitive low-frequency radio observations have revealed that the picture is much more complex, and other types of diffuse source (many of which do not fit our taxonomy) have been detected in recent years (e.g. Govoni et al 2019;Botteon et al 2020a,c;Ignesti et al 2020b;Hodgson et al 2021;Knowles et al 2022;Venturi et al 2022). The extremely large spatial scale of these sources, combined with the short lifetime of the relativistic electrons generating the synchrotron emission (𝜏 10 8 yr) implies in-situ acceleration by physical processes in the ICM.…”

“…With this large field of view (FOV), operating at low frequencies, and with baselines in the range 22 m and 6 km (providing sensitivity to radio emission on a wide range of angular scales), ASKAP is ideally suited to observations of low surface brightness diffuse radio 1 See https://www.narrabri.atnf.csiro.au/people/ste616/ beamshapes/beamshape_16cm.html for details of the ATCA 16 cm band beam model. sources typically found in many clusters of galaxies (HyeongHan et al 2020;Wilber et al 2020;Brüggen et al 2021;Di Mascolo et al 2021;Duchesne et al 2021a,c;Venturi et al 2022).…”

Intracluster Magnetic Filaments and an Encounter with a Radio Jet

“…Ultimately, the seed electrons upon which the reacceleration operates likely come from current or past AGN activity. Whether we can link specific filamentary structures to individual radio galaxies (as in cases where bars directly cross a tailed radio galaxy; Venturi et al 2022;Lame'e 2017;Botteon et al 2020) or where they appear to be the remnants of a dissipating lobe (Brienza et al 2022), or whether multiple AGN contribute to a mixed-background seed population, or whether both play a role, are major open issues.…”