Red Clump Stars from the LAMOST data I: identification and distance
  We present a sample of about 120,000 red clump candidates selected from the
LAMOST DR2 catalog based on the empirical distribution model in the effective
temperature vs. surface gravity plane. Although, in general, red clump stars
are considered as the standard candle, they do not exactly stay in a narrow
range of absolute magnitude, but may extend to more than 1 magnitude depending
on their initial mass. Consequently, conventional oversimplified distance
estimations with assumption of fixed luminosity may lead to systematic bias
related to the initial mass or the age, which may potentially affect the study
of the evolution of the Galaxy with red clump stars. We therefore employ an
isochrone-based method to estimate the absolute magnitude of red clump stars
from their observed surface gravities, effective temperatures, and
metallicities. We verify that the estimation well removes the systematics and
provide an initial mass/age independent distance estimates with accuracy less
than 10%.
