1 research outputs found
Automated identification of 2612 late-k and M dwarfs in the LAMOST commissioining data using the classification template fits
We develop a template-fit method to automatically identify and classify
late-type K and M dwarfs in spectra from the LAMOST. A search of the
commissioning data, acquired in 2009-2010, yields the identification of 2612
late-K and M dwarfs. The template fit method also provides spectral
classification to half a subtype, classifies the stars along the dwarf-subdwarf
metallicity sequence, and provides improved metallicity/gravity information on
a finer scale. The automated search and classification is performed using a set
of cool star templates assembled from the Sloan Digital Sky Survey
spectroscopic database. We show that the stars can be efficiently classified
despite shortcomings in the LAMOST commissioning data which include bright sky
lines in the red. In particular we find that the absolute and relative
strengths of the critical TiO and CaH molecular bands around 7000A are cleanly
measured, which provides accurate spectral typing from late-K to mid-M, and
makes it possible to estimate metallicities in a way that is more efficient and
reliable than with the use of spectral indices or spectral-index based
parameters such as zeta. Most of the cool dwarfs observed by LAMOST are found
to be metal-rich dwarfs. We use a calibration of spectral type to absolute
magnitude and estimate spectroscopic distances for all the stars; we also
recover proper motions from the SUPERBLINK and PPMXL catalogs. Our analysis of
the estimated transverse motions suggests a mean velocity and standard
deviation for the UVW components of velocity to be: U=-9.8 km/s; V=-22.8 km/s;
W=-7.9 km/s. The resulting values are general agreement with previous reported
results, which yields confidence in our spectral classification and
spectroscopic distance estimates, and illustrates the potential for using
LAMOST spectra of K and M dwarfs for investigating the chemo-kinematics of the
local Galactic disk and halo.Comment: 18 pages,16 figures,accepted for publication A