On local dark matter density

Abstract

In 2012, we applied a three-dimensional formulation to kinematic measurements of the Galactic thick disk and derived a surprisingly low dark matter density at the solar position. This result was challenged by Bovy & Tremaine (2012, ApJ, 756, 89), who claimed that the observational data are consistent with the expected dark matter density if a one-dimensional approach is adopted. We analyze the assumption at the bases of their formulation and their claim that this returns a lower limit for the local dark matter density, which is accurate within 20%. We find that the validity of their formulation depends on the underlying mass distribution. We therefore analyze the predictions that their hypothesis casts on the radial gradient of the azimuthal velocity dV/dR and compare it with observational data as a testbed for the validity of their formulation. We find that their hypothesis requires too steep a profile of dV(Z)/dR, which is inconsistent with the observational data both in the Milky Way and in external galaxies. As a consequence, their results are biased and largely overestimate the mass density. Dynamical simulations also show that, contrary to their claims, low values of dV/dR are compatible with a Milky Way like potential with radially constant circular velocity. We nevertheless confirm that, according to their criticism, our assumption dV/dR=0 is only an approximation. If this hypothesis is released, and the available information about dV/dR in the thick disk is used, the resulting local dark matter density increases by a tiny amount, from 0+-1 to 2+-3 mM_sun pc^(-3), with an upper limit of ~3.5 mM_sun pc^(-3). Hence, this approximation has negligible influence on our results. Our analysis shows that their criticism is not a viable explanation for the inferred lack of dark matter at the solar position detected by us. More studies are required to understand these unexpected results.

Accepted for publication in Astronomy & Astrophysics

References in corpus (35)

• The Sloan Digital Sky Survey: Technical Summary
• A Universal Density Profile from Hierarchical Clustering
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• Kinematics of Metal-Poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Non-Kinematically Selected Stars
• The Milky Way Tomography with SDSS: II. Stellar Metallicity
• The spatial structure of mono-abundance sub-populations of the Milky Way disk
• The dark matter density at the Sun's location
• On the local dark matter density
• The local density of matter mapped by Hipparcos
• Unified Rotation Curve of the Galaxy -- Decomposition into de Vaucouleurs Bulge, Disk, Dark Halo, and the 9-kpc Rotation Dip --
• Thin, thick and dark discs in LCDM
• Determination of the Local Dark Matter Density in our Galaxy
• The Proper Motion of SgrA*: I. First VLBA Results
• A new determination of the local dark matter density from the kinematics of K dwarfs
• The Gravitational Potential Near the Sun From SEGUE K-dwarf Kinematics
• Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood
• The vertical motions of mono-abundance sub-populations in the Milky Way disk
• Luminous and Dark Matter in the Milky Way
• The Dark Disk of the Milky Way
• Kinematics of the Outer Stellar Halo
• The Kinematics of Thick Disks in Nine External Galaxies
• Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths
• Vertical distribution of Galactic disk stars : II. The surface mass density in the Galactic plane
• The Kinematics of Thick Disks in External Galaxies
• On the usage of Flaring Gas Layers to determine the Shape of Dark Matter Halos
• Local Surface Density of the Galactic Disk from a 3-D Stellar Velocity Sample
• Limits on the local dark matter density
• The 3D Velocity Structure of the Thick Disk from SPM4 and RAVE DR2
• Velocity Shear of the Thick Disk from SPM3 Proper Motions at the South Galactic Pole
• Kinematical and chemical vertical structure of the Galactic thick disk I. Thick disk kinematics
• No evidence for a dark matter disk within 4 kpc from the Galactic plane
• Metallicity Gradients of Thick Disk Dwarf Stars
• Structure and kinematics of edge-on galaxy discs - I. Observations of the stellar kinematics
• Determining the velocity dispersion of the thick disc
• Transverse gradients of azimuthal velocity in a global disk model of the Milky Way

Cited by in corpus (15)

• The Waning of the WIMP? A Review of Models, Searches, and Constraints
• Dynamical constraints on the dark matter distribution in the Milky Way
• Testing dark matter and geometry sustained circular velocities in the Milky Way with Gaia DR2
• Mixed sneutrino dark matter in light of the 2011 XENON and LHC results
• Galactic Center Radio Constraints on Gamma-Ray Lines from Dark Matter Annihilation
• Updated Kinematic Constraints on a Dark Disk
• $\text{galkin}$: a new compilation of the Milky Way rotation curve data
• The difficulty of measuring the local dark matter density
• Decoherence from General Relativity
• The vertical force in the Solar Neighbourhood using red clump stars in TGASxRAVE - Constraints on the local dark matter density
• Gravitational Focusing and Substructure Effects on the Rate Modulation in Direct Dark Matter Searches
• Jeans analysis of the Galactic thick disk and the local dark matter density
• The Case Against Dark Matter and Modified Gravity: Flat Rotation Curves Are a Rigorous Requirement in Rotating Self-Gravitating Newtonian Gaseous Disks
• Weighing the Galactic disk using the Jeans equation: lessons from simulations
• Mapping dark matter in the Milky Way, a synopsis