Kinematic distances of galaxies in the Local Volume

TL;DR

This study evaluates the accuracy of kinematic distances to nearby galaxies using the Numerical Action Method, comparing them with high-precision TRGB measurements, and finds NAM provides about 20% accurate distances across most of the Local Volume.

Contribution

It demonstrates that NAM distances are consistent with TRGB measurements, establishing NAM as a reliable method for estimating galaxy distances within the Local Volume.

Findings

NAM distances differ from TRGB by about -0.30 Mpc on average.

NAM achieves approximately 20% accuracy for most of the sky.

The method is less accurate near Virgo and Coma-I regions.

Abstract

We consider the kinematic distances to nearby galaxies obtained by the Numerical Action Method (NAM) based on the Cosmic-flow-3 survey data. NAM distances are compared with 418 high-precision distances measured by the Tip of the Red Giant Branch (TRGB) method using the Hubble Space Telescope. We estimated the average difference <D_NAM - D_TRGB> = -0.30 +- 0.08 Mpc and the standard deviation of 1.57 Mpc. Approximately the same difference in the distance scale is obtained in comparison with less accurate distance estimates through the membership of galaxies in known groups or from the Tully-Fisher relation. We conclude that the NAM method provides distance estimates with an accuracy of 20% within the Local Volume, which is valid for ~90% of the sky, except for the regions of the Virgo cluster and the Coma-I group.