Milky Way tomography with the SkyMapper Southern Survey: I: Atmospheric
  parameters and distances of one million red giants
  Accurate determinations of atmospheric parameters (effective temperature
$T_{\rm eff}$, surface gravity log $g$ and metallicity [Fe/H]) and distances
for large complete samples are of vital importance for various Galactic
studies. We have developed a photometric method to select red giant stars and
estimate their atmospheric parameters from the photometric colors provided by
the SkyMapper Southern Survey (SMSS) data release (DR) 1.1, using stars in
common with the LAMOST Galactic spectroscopic surveys as a training set.
Distances are estimated with two different approaches: one based on the Gaia
DR2 parallaxes for nearby ($d \leq 4.5$ kpc) bright stars and another based on
the absolute magnitudes predicted by intrinsic color $(g-i)_0$ and photometric
metallicity [Fe/H] for distant ($d > 4.5$ kpc) faint stars. Various tests show
that our method is capable of delivering atmospheric parameters with a
precision of $\sim$80 K for $T_{\rm eff}$, $\sim$0.18 dex for [Fe/H] and
$\sim$0.35 dex for log $g$, but with a significant systematic error at log $g
\sim$ 2.3. For distances delivered from $(g-i)_0$ and photometric [Fe/H], our
test with the member stars of globular clusters show a median uncertainty of 16
per cent with a negligible zero-point offset. Using this method, atmospheric
parameters and distances of nearly one million red giant stars are derived from
SMSS DR1.1. Proper motion measurements from Gaia DR2 are available for almost
all of the red giant stars, and radial velocity measurements from several large
spectroscopic surveys are available for 44 per cent of these. This sample will
be accessible online at https://yanghuang0.wixsite.com/yangh/research .
