Abstract
We present a statistical study of the filamentary structures of the cosmic web in the large hydro-dynamical simulations Illustris-TNG, Illustris, and Magneticum at redshiftz = 0. We focus on the radial distribution of the galaxy density around filaments detected using the Discrete Persistent Structure Extractor (DisPerSE). We show that the average profile of filaments presents an excess of galaxy density (> 5σ) up to radial distances of 27 Mpc from the core. The relation between galaxy density and the length of filaments is further investigated showing that short (Lf < 9 Mpc) and long (Lf ≥ 20 Mpc) filaments are two statistically different populations. Short filaments are puffier, denser, and more connected to massive objects, whereas long filaments are thinner, less dense, and more connected to less massive structures. These two populations trace different environments and may correspond to bridges of matter between over-dense structures (short filaments), and to cosmic filaments shaping the skeleton of the cosmic web (long filaments). Through Markov chain Monte Carlo (MCMC) explorations, we find that the density profiles of both short and long filaments can be described by the same empirical models (generalised Navarro, Frenk and White,β-model, a single and a double power law) with different and distinct sets of parameters.
Highlights
On its largest scales, matter in the Universe is not distributed uniformly: it is organised in clusters, filaments, walls, and voids
Matter in the Universe is not distributed uniformly: it is organised in clusters, filaments, walls, and voids. These structures form the cosmic web (Bond et al 1996), that is a gigantic network of dark matter and gas, which formed under the effect of gravity from the anisotropic collapse of initial fluctuations of the density field (Zel’dovich 1970)
The cosmic web was first observed in the Center for Astrophysics (CfA) galaxy survey by de Lapparent et al (1986) and since has drawn a lot of attention in both observational and simulation fields
Summary
Matter in the Universe is not distributed uniformly: it is organised in clusters, filaments, walls, and voids. For example, the Sloan Digital Sky Survey (SDSS, York et al 2000), the two degree Field Galaxy Redshift Survey (2dFGRS, Colless et al 2003), the Cosmic Evolution Survey (COSMOS, Scoville et al 2007), the 6dF Galaxy Survey (6dFGS, Jones et al 2009), the Galaxy and Mass Assembly (GAMA, Driver et al 2011), and the VIMOS VLT deep survey (Le Fèvre et al 2005, VVDS) VIPERS (Guzzo et al 2014) and SAMI (Bryant et al 2015) surveys All of these observations have shown galaxies distributed in filamentary structures, exhibiting the filamentary pattern of the cosmic web
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