Speaker
Description
Most of the ‘missing’ baryons in the local Universe are expected to reside in some diffuse gas phase of the intergalactic medium. In fact, recent results from X-ray absorption studies and Fast Radio Bursts indicate that all the baryons are essentially accounted for, but it remains to be determined exactly where they lie. Studies that cross-correlate galaxies with the thermal Sunyaev-Zel’dovich (tSZ) maps from Planck indicate that up to 50% of the baryons may be spread throughout filamentary structures in superclusters at low redshift. A wide-area rotation measure (RM) Grid is able to reveal ionised and magnetised gas in the outskirts of a galaxy cluster beyond that typically probed by X-rays. We use the RM catalog from the POSSUM Pilot 2 survey of the Shapley supercluster, from both Band 1 and 2, as well as Planck maps of the tSZ effect, in an attempt to map the diffuse magneto-ionic material extending from the individual galaxy clusters and into the connecting filamentary structures. The Shapley supercluster (z~0.05) contains the largest concentration of Abell clusters (~25) in the local Universe, spread over 100’s of Mpc and 10’s of degrees on the sky. The distribution of clusters displays a complex morphology, with walls and filaments of galaxies extending from the three main interacting Abell clusters (A3556-A3558-A3562). It provides an ideal laboratory to study the diffuse gas expected to permeate these structures. In particular, we are able to probe the magnetic field in the region between the two most massive clusters of the supercluster, namely, A3562 and A3558.
