Evidence for dark matter in the inner Milky Way...Really?

TL;DR

This paper critiques recent claims of dark matter detection in the Milky Way by showing the observed discrepancies are consistent with modified gravity theories rather than dark matter.

Contribution

It demonstrates that the claimed evidence for dark matter can be explained by known gravitational anomalies and modified gravity, challenging the original interpretation.

Findings

Discrepancies are due to gravitational anomalies at low accelerations.

Modified gravity models can reproduce observed rotation curves.

Original dark matter evidence is not conclusive.

Abstract

The following is a comment on the recent letter by Iocco et al. (2015, arXiv:1502.03821) where the authors claim to have found "...convincing proof of the existence of dark matter...". The letter in question presents a compilation of recent rotation curve observations for the Milky Way, together with Newtonian rotation curve estimates based on recent baryonic matter distribution measurements. A mismatch between the former and the latter is then presented as "evidence for dark matter". Here we show that the reported discrepancy is the well known gravitational anomaly which consistently appears when dynamical accelerations approach the critical Milgrom acceleration a_0 = 1.2 \times 10^{-10} m / s^2. Further, using a simple modified gravity force law, the baryonic models presented in Iocco et al. (2015), yield dynamics consistent with the observed rotation values.