The dark matter density at the Sun’s location

¹ SISSA/ISAS, via Beirut 2-4, 34013 Trieste, Italy
e-mail: salucci@sissa.it
² Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, Italy
³ Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, CP 226, Bvd du Triomphe, 1050 Bruxelles, Belgium, Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, 9000 Gent, Belgium
⁴ Universidade Federal do ABC, Rua Catequese 242, 09090-400 Santo André-São Paulo, Brasil

Received: 8 March 2010
Accepted: 17 June 2010

Abstract

Aims. We derive the value of the dark matter density at the Sun’s location (ρ_⊙) without fully modeling the mass distribution in the Galaxy.

Methods. The proposed method relies on the local equation of centrifugal equilibrium and is independent of i) the shape of the dark matter density profile, ii) knowledge of the rotation curve from the galaxy center out to the virial radius, and iii) the uncertainties and the non-uniqueness of the bulge/disk/dark halo mass decomposition.

Results. The result can be obtained in analytic form, and it explicitly includes the dependence on the relevant observational quantities and takes their uncertainties into account. By adopting the reference, state-of-the-art values for these, we find ρ_⊙ = 0.43(11)(10) GeV/cm³, where the quoted uncertainties are respectively due to the uncertainty in the slope of the circular-velocity at the Sun location and the ratio between this radius and the length scale of the stellar exponential thin disk.

Conclusions. We obtained a reliable estimate of ρ_⊙, that, in addition has the merit of being ready to take any future change/improvement into account in the measures of the observational quantities it depends on.