Simulating the physical properties of dark matter and gas inside the cosmic web

Using the results of a high‐resolution, cosmological hydrodynamical re‐simulation of a supercluster‐like region, we investigate the physical properties of the gas located along the filaments and bridges which constitute the so‐called cosmic web. First, we analyse the main characteristics of the density, temperature and velocity fields, which have quite different distributions, reflecting the complex dynamics of the structure‐formation process. Then we quantify the signals which originate from the matter in the filaments by considering different observables. Inside the cosmic web, we find that the halo density is about 10–14 times larger than cosmic mean; the bremsstrahlung X‐ray surface brightness reaches at most 10 −16 erg s −1 cm −2 arcmin −2 ; the Compton‐ y parameter due to the thermal Sunyaev–Zel'dovich effect is about 10 −6 ; the reduced shear produced by the weak lensing effect is ∼0.01–0.02. These results confirm the difficulty of an observational detection of the cosmic web. Finally, we find that projection effects of the filamentary network can affect the estimates of the properties of single clusters, increasing their X‐ray luminosity by less than 10 per cent and their central Compton‐ y parameter by up to 30 per cent.