title: Universal density profile for cosmic voids.
abstract: We present a simple empirical function for the average density profile of cosmic voids, identified via the watershed technique in ΛCDM N-body simulations. This function is universal across void size and redshift, accurately describing a large radial range of scales around void centers with only two free parameters. In analogy to halo density profiles, these parameters describe the scale radius and the central density of voids. While we initially start with a more general four-parameter model, we find two of its parameters to be redundant, as they follow linear trends with the scale radius in two distinct regimes of the void sample, separated by its compensation scale. Assuming linear theory, we derive an analytic formula for the velocity profile of voids and find an excellent agreement with the numerical data as well. In our companion paper [Sutter et al., arXiv:1309.5087 [Mon. Not. R. Astron. Soc. (to be published)]], the presented density profile is shown to be universal even across tracer type, properly describing voids defined in halo and galaxy distributions of varying sparsity, allowing us to relate various void populations by simple rescalings. This provides a powerful framework to match theory and simulations with observational data, opening up promising perspectives to constrain competing models of cosmology and gravity.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France and CNRS, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France.
authors.forename: Nico
authors.initials: N
authors.lastname: Hamaus
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France and CNRS, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France and Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: P M
authors.initials: PM
authors.lastname: Sutter
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France and CNRS, UMR 7095, Institut d'Astrophysique de Paris, F-75014 Paris, France and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Wandelt