The underlying radial acceleration relation

Abstract

The radial acceleration relation (RAR) of late-type galaxies relates their dynamical acceleration, gobs, to that sourced by baryons alone, gbar, across their rotation curves. Literature fits to the RAR have fixed the galaxy parameters on which the relation depends – distance, inclination, luminosity, and mass-to-light ratios – to their maximum a priori values with an uncorrelated Gaussian contribution to the uncertainties in gbar and gobs. In reality these are free parameters of the fit, contributing systematic rather than statistical error. Assuming a range of possible functional forms for the relation with or without intrinsic scatter (motivated by modified Newtonian dynamics with or without the external field effect), I use Hamiltonian Monte Carlo to perform the full joint inference of RAR and galaxy parameters for the Spitzer Photometry and Accurate Rotation Curves (SPARC) dataset. This reveals the intrinsic RAR underlying that observed. I find an acceleration scale $a_0=(1.19 \pm 0.04 \, \text{(stat)} \pm 0.09 \, \text{(sys)}) \: \times \: 10^{-10}$ m s−2, an intrinsic scatter $\sigma _\text{int}=(0.034 \pm 0.001 \, \text{(stat)} \pm 0.001 \, \text{(sys)})$ dex (assuming the SPARC error model is reliable), and weak evidence for the external field effect. I make summary statistics of all my analyses publicly available for future SPARC studies or applications of a calibrated RAR, for example direct distance measurement.

Towards galaxy cluster models in Aether-Scalar-Tensor theory: isothermal spheres and curiosities

“…MOND implies an algebraic relation between the acceleration expected from the baryons only, a N , and the observed acceleration a obs . In the context of rotation curves of disk galaxies this relation is known as the Radial Acceleration Relation (RAR) and it is observationally supported by the rotation curves of a large sample of disk galaxies [21]; see [22] and [23] for recent studies. The observational support for the RAR has recently been extended by about two orders of magnitude in acceleration using weak lensing [24,25] in place of baryonic tracers, consistent with the deep MOND scaling of the acceleration a obs ∼ √ a N to a previously JCAP04(2024)040…”