Searching for a possible dipole anisotropy on acceleration scale with 147 rotationally supported galaxies

TL;DR

This study investigates potential dipole anisotropy in the acceleration scale using 147 galaxies, finding significant dipole signals aligned with previous anisotropy directions, but results are inconclusive due to limited data.

Contribution

It introduces a dipole correction to the radial acceleration relation, revealing anisotropy in the acceleration scale with a significant dipole magnitude based on observational data.

Findings

Dipole magnitude of 0.25±0.04 in acceleration scale.

Dipole direction aligned with previous anisotropy findings.

Robust checks show the anisotropy is not due to isotropic mock data.

Abstract

We report a possible dipole anisotropy on acceleration scale $g_{\dag}$ with 147 rotationally supported galaxies in local Universe. It is found that a monopole and dipole correction for the radial acceleration relation can better describe the SPARC data set. The monopole term is negligible but the dipole magnitude is significant. It is also found that the dipole correction is mostly induced by the anisotropy on the acceleration scale. The magnitude of $\hat{g}_{\dag}$-dipole reaches up to $0.25\pm0.04$, and its direction is aligned to $(l,b) = (171.30^{\circ}\pm7.18^{\circ}, -15.41^{\circ}\pm4.87^{\circ})$, which is very close to the maximum anisotropy direction from the hemisphere comparison method. Furthermore, robust check shows that the dipole anisotropy couldn't be reproduced by isotropic mock data set. However, it is still premature to claim that the Universe is anisotropic due to the small data samples and uncertainty in the current observations.