On the relationship between a giant radio galaxy MSH 05-22 and the ambient large-scale galaxy structure

Abstract

We present a comparison of the properties of a giant radio galaxy and the ambient intergalactic medium, whose properties are inferred from the large-scale distribution in galaxies. The double lobes of the radio galaxy MSH 05-22 are giant--1.8 Mpc projected linear size--and interacting with the environment outside the interstellar medium and coronal halo associated with the host galaxy. The radio lobes appear to be relicts and the double structure is asymmetric. We have examined the large-scale structure in the galaxy distribution surrounding the radio source. The host galaxy of MSH 05-22 is associated with a small group that lies close to the boundary of sheet-like and filamentary density enhancements, and adjacent to a void. Assuming that the galaxies trace gas, the asymmetries in the radio morphology in this case study appear related to the anisotropy in the medium. However, the observed overdensities and structure formation models for the heating of the intergalactic medium (IGM) suggest a density-temperature product for the IGM environment that is an order of magnitude below that expected from the properties of the radio source. The discordance suggests that even sources like MSH 05-22, which are observed in the relatively low-density IGM environment associated with the filamentary large-scale structure and have multiple signatures of being relicts, may be overpressured and evolving towards an equilibrium relaxed state with the ambient IGM. Alternately, it is speculated that astrophysical feedback originating in galaxy overdensities observed 1-2 Mpc to the N and NE of MSH 05-22 might be the mechanism for the heating of the ambient IGM gas.