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

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_(obs), the observed circular acceleration of the galaxy, and g_(bar), the acceleration due to the total baryonic mass of the galaxy. For accelerations above 10^(10) m s^(-2), g_(obs), traces g_(bar), asymptoting to the 1:1 line. Below this scale, there is a break in the relation such that g_(obs) ~ g_(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 Cold Dark Matter (CDM) theory) lie on the RAR if we simply require that their rotation curves satisfy the BTFR. We explore conditions needed to break this degeneracy: subkiloparsec resolved rotation curves inside of cored DM-dominated profiles and/or outside ≫ 100 kpc could lie on BTFR but deviate in the RAR, providing new constraints on DM.