KINEMATICAL AND CHEMICAL VERTICAL STRUCTURE OF THE GALACTIC THICK DISK. II. A LACK OF DARK MATTER IN THE SOLAR NEIGHBORHOOD,

By C. M. Bidin, Giovanni Carraro, R. Méndez, Rory Smith. 2012

95 citations recorded by the source corpus.

We estimated the dynamical surface mass density Σ at the solar position between Z = 1.5 and 4 kpc from the Galactic plane, as inferred from the kinematics of thick disk stars. The formulation is exact within the limit of validity of a few basic assumptions. The resulting trend of Σ(Z) matches the expectations of visible mass alone, and no dark component is required to account for the observations. We extrapolate a dark matter (DM) density in the solar neighborhood of 0 ± 1 mM☉ pc−3, and all the current models of a spherical DM halo are excluded at a confidence level higher than 4σ. A detailed analysis reveals that a small amount of DM is allowed in the volume under study by the change of some input parameter or hypothesis, but not enough to match the expectations of the models, except under an exotic combination of non-standard assumptions. Identical results are obtained when repeating the calculation with kinematical measurements available in the literature. We demonstrate that a DM halo would be detected by our method, and therefore the results have no straightforward interpretation. Only the presence of a highly prolate (flattening q > 2) DM halo can be reconciled with the observations, but this is highly unlikely in ΛCDM models. The results challenge the current understanding of the spatial distribution and nature of the Galactic DM. In particular, our results may indicate that any direct DM detection experiment is doomed to fail if the local density of the target particles is negligible.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

Constraining the Galaxy's dark halo with RAVE stars (2014, methodology): “Bovy & Tremaine (2012) showed that the analysis in Moni Bidin et al. (2012b) is flawed, and from the data in Moni Bidin et al. (2012a) derived a value for ρdm, that is consistent with a significant dark halo.”
The Local Dark Matter Density (2012, methodology): “Finally, it is worth discussing the claim by Bidin et al. (2012).”
Galactic Searches for Dark Matter (2012, background): “ese stars have the benet of being old and dynamically well-mixed. In an earlier study Holmberg and Flynn (2000) utilized a sample of A-F stars, which are typically not as old. The recent analysis of Bidin et al. (2012) utilized a sample of approximately 400 thick disk red giants towards the South Ga”
The local dark matter density (2014, background): “Local measures use the vertical kinematics of stars near the Sun – called ‘tracers’ (e.g. Kapteyn, 1922; Oort, 1932; Hill, 1960; Oort, 1960; Bahcall, 1984b,a; Bienayme et al., 1987; Kuijken & Gilmore, 1989c,b,a, 1991; Bahcall et al., 1992; Creze et al., 1998; Holmberg & Flynn, 2000a; Siebert et al.,”
ON THE LOCAL DARK MATTER DENSITY (2012, methodology): “In contrast to the data from Moni Bidin et al. (2012a), the SEGUE volume selection is known in detail (e.g., Bovy et al. 2012b) so both the spatial structure and kinematics can be obtained for the same set of tracer stars.”
STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “…the cleanest determination of the local density of dark matter is that of Bovy & Tremaine (2012; hereafter BT12), who analyzed the data of Moni Bidin et al. (2012a, 2012b) on stars far enough above the plane (1–4 kpc) that the variation of gravitational acceleration with height is almost…”