Letter to the Editor

Turnaround density as a probe of the cosmological constant

¹ Department of Physics and Institute for Theoretical and Computational Physics, University of Crete, 70013 Heraklio, Greece
e-mail: pavlidou@physics.uoc.gr
² Institute of Astrophysics, Foundation for Research and Technology – Hellas, Vassilika Vouton, 70013 Heraklio, Greece
³ Department of Astronomy and Astrophysics and KICP, University of Chicago, Chicago, IL 60637, USA

Received: 19 December 2019
Accepted: 20 April 2020

Abstract

Spherical collapse predicts that a single value of the turnaround density, meaning the average matter density within the scale on which a structure detaches from the Hubble flow, characterizes all cosmic structures at the same redshift. It was recently shown by Korkidis et al. that this feature persists in complex non-spherical galaxy clusters that have been identified in N-body simulations. Here we show that the low-redshift evolution of the turnaround density constrains the cosmological parameters and it can be used to derive a local constraint on Ω_Λ, 0 alone, independent of Ω_m, 0. The turnaround density thus offers a promising new method for exploiting upcoming large cosmological datasets.