Cosmic Web properties for radio galaxies

With the BORG SDSS tidal tensor, we also measured for each RG whether the gravitational dynamics of its Cosmic Web environment resemble those of clusters, filaments, sheets, or voids. For both luminous giants and general RGs, the Cosmic Web density distribution is gamma distribution-like. Luminous giants populate large-scale environments that tend to be denser than those of general RGs.

This result is corroborated by gravitational dynamics classification and a cluster catalogue crossmatching analysis. We find that the Cosmic Web density around RGs with 150 MHz radio luminosity l_{nu}_ is distributed as 1+{DELTA}_RG_|L_{nu}_=l_{nu}_~{GAMMA}(k,{theta}), where k=4.8+0.2.l, {theta}=1.4+0.02.L, and L:=log10(l_{nu}_(10^23^W/Hz)^-1^). This work presents more than a thousand inferred megaparsec-scale densities around radio galaxies, which may be correct up to a factor of order unity - except in clusters of galaxies, where the densities can be more than an order of magnitude too low.

We pave the way to a future in which megaparsec-scale densities around RGs are common inferred quantities, which help to better understand their dynamics, morphology, and interaction with the enveloping Cosmic Web. Our data demonstrate that luminous giants inhabit denser environments than general RGs. This shows that - at least at high jet powers - low-density environments are no prerequisite for giant growth.

Using general RGs, we quantified the relation between radio luminosity at 150MHz and Cosmic Web density on a smoothing scale of ~2.9Mpc/h. This positive relation, combined with the discrepancy in radio luminosity between known giants and general RGs, reproduces the discrepancy in Cosmic Web density between known giants and general RGs. Our findings are consistent with the view that giants are regular, rather than mechanistically special, members of the radio galaxy population.