Action Dynamics of the Local Supercluster

TL;DR

This paper models the nonlinear gravitational trajectories of galaxies in the Local Supercluster using a Numerical Action Method constrained by observational data, revealing detailed mass distributions and orbital histories.

Contribution

It introduces a comprehensive NAM-based model incorporating external inhomogeneities and provides new estimates of masses and orbital dynamics within the Local Supercluster.

Findings

Model fits velocity flow well with low median chi-square.

Estimated masses for Virgo, MW, and M31 are provided.

Constructed 3D orbital histories explain peculiar motions.

Abstract

The fully nonlinear gravitationally induced trajectories of a nearly complete set of galaxies, groups, and clusters in the Local Supercluster are constructed in a Numerical Action Method (NAM) model constrained by data from the CosmicFlows survey and various distance indicators. We add the gravity field due to inhomogeneities external to the sample sphere by making use of larger scale peculiar flow measurements. Assignments of total masses were made to find the best overall set of mutual attractions, as determined by a goodness criterion based on present day radial velocities, individually for the Virgo Cluster, M31, and the Milky Way (MW), and via a mass-to-light ratio relationship for other masses. The low median chi-square found indicates the model fits the present day velocity flow well, but a slightly high mean chi-square may indicate that some masses underwent complex orbits. The best fit, when setting the value of $H_0$ to the CosmicFlows value of 75 km/s/Mpc and the WMAP value for $\Omega_m=0.244$ consistent with that $H_0$, occurs with the following parameters: $\Omega_{orphan} = 0.077\pm0.016$, $M/L_K $= $40 \pm 2$ $L_{10}^{0.15}$ $M_\odot/L_\odot$ ($L_{10}$ is K-band luminosity in units of $10^{10} L_\odot$), a Virgo mass of $6.3\pm0.8 \times 10^{14} M_\odot$ ($M/L_K = 113\pm15 M_\odot/L_\odot$), and a mass for the MW plus M31 of $5.15\pm0.35 \times 10^{12} M_\odot$. The best constant mass-to-light ratio is $M/L_K = 58\pm3 M_\odot/L_\odot$. The Virgocentric turnaround radius is $7.3\pm0.3$ Mpc. We explain several interesting trends in peculiar motions for various regions now that we can construct the 3D orbital histories.