Clusters have edges: the projected phase-space structure of SDSS redMaPPer clusters. Issue 1 (23rd September 2020)

• Record Type: Journal Article
• Authors: Tomooka, Paxton; Rozo, Eduardo; Wagoner, Erika L; Aung, Han; Nagai, Daisuke; Safonova, Sasha
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 499:Issue 1(2020)
• Page Start: 1291
• Page End: 1299
• Publication Date: 2020-09-23
• Subjects: galaxies: clusters: general -- galaxies: haloes -- dark matter -- large-scale structure of Universe; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2841
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We study the distribution of line-of-sight velocities of galaxies in the vicinity of Sloan Digital Sky Survey (SDSS) red-sequence Matched-filter Probabilistic Percolation (redMaPPer) galaxy clusters. Based on their velocities, galaxies can be split into two categories: galaxies that are dynamically associated with the cluster, and random line-of-sight projections. Both the fraction of galaxies associated with the galaxy clusters, and the velocity dispersion of the same, exhibit a sharp feature as a function of radius. The feature occurs at a radial scale R edge ≈ 2.2 R λ, where R λ is the cluster radius assigned by redMaPPer. We refer to R edge as the 'edge radius'. These results are naturally explained by a model that further splits the galaxies dynamically associated with a galaxy cluster into a component of galaxies orbiting the halo and an infalling galaxy component. The edge radius R edge constitutes a true 'cluster edge', in the sense that no orbiting structures exist past this radius. A companion paper tests whether the 'halo edge' hypothesis holds when investigating the full three-dimensional phase-space distribution of dark matter substructures in numerical simulations, and demonstrates that this radius coincides with a suitably defined splashback radius.