S317p.77 — Measure the local dark matter density with LAMOST spectroscopic survey

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Aug 4th at 6:00 PM until 6:00 PM

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Author(s): Chao Liu1, Qiran Xia1, Shude Mao1

Institution(s): 1. national astronomical observatories, CAS

The local dark matter density plays the key role in the distribution of the dark matter halo near the Galactic disk. It will also answer whether a dark matter disk exists in the Milky Way. We measure the local dark matter density with LAMOST observed stars located at around the north Galactic pole. The selection effects of the observations are well considered and corrected. The data is split out into lots of sub-populations in the dimensions of the absolute magnitude and metallicity. The vertical density profile of each sub-population is a single exponential so that an analytical model can be used to derive the local DM density. We find that the derived DM density, which is around 0.015 Msun/pc3, is very sensitive to the selection effects of the observation. Several tests based on the real and mock data have been done to investigate the influences of the observational selection effects, including the volume incompleteness due to the limiting magnitude, the coverage in the vertical height and the Galactocentric radius of the observed data, and the transition of the stellar populations along the vertical height etc. We conclude that the improper selections of the data can significantly alter the determined value of the local DM density. We therefore suggest that the observed data must be carefully handled and well matches the corresponding dynamical model.