Line-of-sight acceleration as a test of the Galactic Yukawa potential

TL;DR

This study explores how precise radial acceleration measurements of stars and globular clusters can test modifications to gravity, specifically the Yukawa potential, in the Milky Way, highlighting the potential of RR Lyrae stars for strong constraints.

Contribution

It demonstrates that radial acceleration measurements of RR Lyrae stars can provide competitive constraints on the Yukawa potential, comparable to rotation curve data, with next-generation spectrographs.

Findings

Next-generation spectrographs are insufficient for globular cluster constraints.

RR Lyrae stars can yield strong Yukawa constraints at 10 cm/s precision.

Rotation curve data remains competitive unless measurement precision improves significantly.

Abstract

We forecast the impact of direct radial acceleration measurements, based on two redshift measurements of the same target one decade apart, on constraining the Yukawa correction to the Newtonian potential in the Milky Way. The Galaxy's matter distribution is modeled as the sum of a spherical bulge, a spherical dark matter halo, and two axially symmetric disks. Considering a sample of 165 Milky Way globular clusters, we find that the precision of next-generation spectrographs ($\sim$ 10 cm s$^{-1}$) is not sufficient to provide competitive constraints compared to rotation curve data using the same baryonic matter distribution. The latter sample only becomes competitive for a precision better than 0.6 cm s$^{-1}$. On the other hand, we find that adopting a population of $1.3 \times 10^5$ RR Lyrae stars as targets, a precision of $\sim$ 10 cm s$^{-1}$ can achieve constraints on the Yukawa parameters as strong as with the rotation curves.