Hubble flow around Fornax cluster of galaxies

TL;DR

This study estimates the mass of the Fornax galaxy cluster and its surrounding complex using the zero-velocity surface method, avoiding equilibrium assumptions, and analyzes galaxy velocities within 20 Mpc.

Contribution

It introduces a mass estimation approach based on the zero-velocity surface that does not rely on equilibrium assumptions, suitable for a system still in formation.

Findings

Mass of Fornax cluster within 2.62-5.18 Mpc is (0.40-3.32) x 10^14 solar masses.

Mass of the Fornax-Eridanus complex within 3.88-5.60 Mpc is (1.30-3.93) x 10^14 solar masses.

Velocity field mapped using 109 galaxies with high distance accuracy.

Abstract

Aims. This work aims to provide a new mass estimate for the Fornax cluster and the Fornax-Eridanus complex, avoiding methods like the virial or fits of X-ray emission profile, which assume that the system is in equilibrium, probably not the case of Fornax, still in process of formation. Methods. Our mass estimate is based on the determination of the zero-velocity surface which, in the context of the spherical infall model permits an evaluation of the total mass inside such a surface. The zero-velocity surface radius R0 was estimated either by a running median procedure or by fitting the data to the velocity field expected from the spherical model, including effects of the cosmological constant. The velocity field in a region within 20 Mpc of the Fornax center was mapped using a list of 109 galaxies whose distances have an average accuracy of 0.31 mag in their distance modulus. Results. Our analysis indicates that the mass of the Fornax cluster itself inside a radius of [2.62-5.18] Mpc is [0.40-3.32] \times 10^14 Modotwhile the mass inside [3.88-5.60] Mpc, corresponding to the Fornax-Eridanus complex is [1.30-3.93] \times 10^14 M\odot.