Determining the local dark matter density with LAMOST data

TL;DR

This study estimates the local dark matter density using LAMOST data and a vertical Jeans equation approach, addressing previous discrepancies and analyzing uncertainties and systematic effects.

Contribution

It provides a new measurement of the local dark matter density with a carefully selected stellar sample and detailed consideration of observational effects.

Findings

Total surface mass density: 78.7 M_sun/pc^2 up to 1 kpc

Local dark matter density: 0.0159 M_sun/pc^3

Sampling density significantly affects the uncertainty

Abstract

Measurement of the local dark matter density plays an important role in both Galactic dynamics and dark matter direct detection experiments. However, the estimated values from previous works are far from agreeing with each other. In this work, we provide a well-defined observed sample with 1427 G \& K type main-sequence stars from the LAMOST spectroscopic survey, taking into account selection effects, volume completeness, and the stellar populations. We apply a vertical Jeans equation method containing a single exponential stellar disk, a razor thin gas disk, and a constant dark matter density distribution to the sample, and obtain a total surface mass density of $\rm {78.7 ^{+3.9}_{-4.7}\ M_{\odot}\ pc^{-2}}$ up to 1 kpc and a local dark matter density of $0.0159^{+0.0047}_{-0.0057}\,\rm M_{\odot}\,\rm pc^{-3}$. We find that the sampling density (i.e. number of stars per unit volume) of the spectroscopic data contributes to about two-thirds of the uncertainty in the estimated values. We discuss the effect of the tilt term in the Jeans equation and find it has little impact on our measurement. Other issues, such as a non-equilibrium component due to perturbations and contamination by the thick disk population, are also discussed.