Signatures in a giant radio galaxy of a cosmological shock wave at intersecting filaments of galaxies

Sensitive images of low-level, megaparsec-sized radio cocoons offer new opp ortunities to probe large-scale intergalactic gas flows outside clusters of galaxies. New radio images of high surface brightness sensitivity at strat egically chosen wavelengths of the giant radio galaxy NGC 315 reveal signif icant asymmetries and particularities in the morphology, radio spectrum, an d polarization of the ejected radio plasma. We argue that the combination o f these signatures provides a sensitive probe of an environmental shock wav e. Analysis of optical redshifts in NGC 315's vicinity confirms its locatio n to be near, or at, a site of large-scale flow collisions in the 100 Mpc s ized Pisces-Perseus supercluster region. NGC 315 resides at the intersectio n of several galaxy filaments, and its radio plasma serves there as a "weat her station," probing the flow of the elusive and previously invisible inte rgalactic medium gas. If our interpretation is correct, this is the first i ndication for a shock wave in flows caused by the cosmological large-scale structure formation, which is located in a filament of galaxies. The possib ility that the putative shock wave is a source of gamma rays and ultrahigh- energy cosmic rays is briefly discussed.