Stars, Gas, and Dark Matter in the Solar Neighborhood
  The surface density and vertical distribution of stars, stellar remnants, and
gas in the solar vicinity form important ingredients for understanding the star
formation history of the Galaxy as well as for inferring the local density of
dark matter by using stellar kinematics to probe the gravitational potential.
In this paper we review the literature for these baryonic components, reanalyze
data, and provide tables of the surface densities and exponential scale heights
of main sequence stars, giants, brown dwarfs, and stellar remnants. We also
review three components of gas (H2, HI, and HII), give their surface densities
at the solar circle, and discuss their vertical distribution. We find a local
total surface density of M dwarfs of 17.3 pm 2.3 Mo/pc^2. Our result for the
total local surface density of visible stars, 27.0 pm 2.7 Mo/pc^2, is close to
previous estimates due to a cancellation of opposing effects: more mass in M
dwarfs, less mass in the others. The total local surface density in white
dwarfs is 4.9 pm 0.6 Mo/pc^2; in brown dwarfs, it is ~1.2 Mo/pc^2. We find that
the total local surface density of stars and stellar remnants is 33.4 pm 3
Mo/pc^2, somewhat less than previous estimates. We analyze data on 21 cm
emission and absorption and obtain good agreement with recent results on the
local amount of neutral atomic hydrogen obtained with the Planck satellite. The
local surface density of gas is 13.7 pm 1.6 Mo/pc^2. The total baryonic mass
surface density that we derive for the solar neighborhood is 47.1 pm 3.4
Mo/pc^2. Combining these results with others' measurements of the total surface
density of matter within 1-1.1 kpc of the plane, we find that the local density
of dark matter is 0.013 pm 0.003Mo/pc^3.The local density of all matter is
0.097 pm 0.013 Mo/pc^3. We discuss limitations on the properties of a possible
thin disk of dark matter.
