The M-giant star candidates identified in the LAMOST data release 1

TL;DR

This paper develops a spectral classification method to identify and catalog M giant stars from LAMOST DR1 data, providing a large, reliable M giant catalog with distance and velocity estimates, and also catalogs M dwarfs/subdwarfs.

Contribution

It introduces an extended M-type templates library and an automated classification pipeline for M giants, improving identification accuracy and catalog completeness.

Findings

Catalog of 8,639 M giants with distances and velocities.

Identification of 101,690 M dwarfs/subdwarfs.

Reliable spectral features and classification accuracy.

Abstract

We perform a discrimination procedure with the spectral index diagram of TiO5 and CaH2+CaH3 to separate M giants from M dwarfs. Using the M giant spectra identified from the LAMOST DR1 with high signal-to-noise ratio (SNR), we have successfully assembled a set of M giant templates, which show more reliable spectral features. Combining with the M dwarf/subdwarf templates in Zhong et al. (2015), we present an extended M-type templates library which includes not only M dwarfs with well-defined temperature and metallicity grid but also M giants with subtype from M0 to M6. Then, the template-fit algorithm were used to automatically identify and classify M giant stars from the LAMOST DR1. The result of M giant stars catalog is cross-matched with 2MASS JHKs and WISE W1/W2 infrared photometry. In addition, we calculated the heliocentric radial velocity of all M giant stars by using the cross-correlation method with the template spectrum in a zero-velocity restframe. Using the relationship between the absolute infrared magnitude MJ and our classified spectroscopic subtype, we derived the spectroscopic distance of M giants with uncertainties of about 40%. A catalog of 8639 M giants is provided. As an additional search result, we also present 101690 M dwarfs/subdwarfs catalog which were classified by our classification pipeline.