The radial acceleration relation is a natural consequence of the baryonic Tully-Fisher relation

TL;DR

This paper demonstrates that the Radial Acceleration Relation (RAR) naturally follows from the baryonic Tully-Fisher relation (BTFR), linking galaxy dynamics with baryonic mass, and explores conditions where deviations could inform dark matter properties.

Contribution

The study shows that the RAR's features are direct consequences of the BTFR and that galaxies with diverse profiles align on the RAR if they satisfy the BTFR, offering new insights into dark matter constraints.

Findings

RAR slope and scatter are derived from the BTFR.

Galaxies with various profiles follow the RAR if they satisfy the BTFR.

Deviations in RAR can occur in specific dark matter profiles, constraining dark matter models.

Abstract

Galaxies covering several orders of magnitude in stellar mass and a variety of Hubble types have been shown to follow the "Radial Acceleration Relation" (RAR), a relationship between $g_{\rm obs}$, the observed circular acceleration of the galaxy, and $g_{\rm bar}$, the acceleration due to the total baryonic mass of the galaxy. For accelerations above $10^{10}~{\rm m \, s}^{-2}$, $g_{\rm obs}$ traces $g_{\rm bar}$, asymptoting to the 1:1 line. Below this scale, there is a break in the relation such that $\rm g_{\rm obs} \sim g_{\rm bar}^{1/2}$. We show that the RAR slope, scatter and the acceleration scale are all natural consequences of the well-known baryonic Tully-Fisher relation (BTFR). We further demonstrate that galaxies with a variety of baryonic and dark matter (DM) profiles and a wide range of dark halo and galaxy properties (well beyond those expected in CDM) lie on the RAR if we simply require that their rotation curves satisfy the BTFR. We explore conditions needed to break this degeneracy: sub-kpc resolved rotation curves inside of "cored" DM-dominated profiles and/or outside $\gg 100\,$kpc could lie on BTFR but deviate in the RAR, providing new constraints on DM.