An estimate of the DM profile in the Galactic bulge region

Abstract

We present an analysis of the mass distribution in the region of the Galactic bulge, which leads to constraints on the total amount and distribution of Dark Matter (DM) therein. Our results – based on the dynamical measurement of the BRAVA collaboration – are quantitatively compatible with those of a recent analysis, and generalized to a vast sample of observationally inferred morphologies of the stellar components in the region of the Galactic bulge. By fitting the inferred DM mass to a generalized NFW profile, we find that cores (γ≲0.6) are forbidden only for very light configurations of the bulge, and that cusps (γ≳1.2) are allowed, but not necessarily preferred. Interestingly, we find that the results for the bulge region are compatible with those obtained with dynamical methods (based on the rotation curve) applied to outer regions of the Milky Way, for all morphologies adopted. We find that the uncertainty on the shape of the stellar morphology heavily affects the determination of the DM distribution in the bulge region, which is gravitationally dominated by baryons, adding up to the uncertainty on its normalization. The combination of the two hinders the actual possibility to infer sound conclusions about the distribution of DM in the region of the Galactic bulge, and only future observations of the stellar census and dynamics in this region will bring us closer to a quantitatively more definite answer.