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J/AJ/150/42          Catalog of 2612 M dwarfs from LAMOST         (Zhong+, 2015)

Automated identification of 2612 late-K and M dwarfs in the LAMOST commissioning data using classification template fits. Zhong J., Lepine S., Hou J., Shen S., Yuan H., Huo Z., Zhang H., Xiang M., Zhang H., Liu X. <Astron. J., 150, 42 (2015)> =2015AJ....150...42Z
ADC_Keywords: Stars, dwarfs ; Stars, M-type ; Spectral types ; Proper motions ; Photometry, infrared Keywords: methods: data analysis - stars: kinematics and dynamics - stars: low-mass - surveys Abstract: We develop a template-fit method to automatically identify and classify late-type K and M dwarfs in spectra from the Large Sky Area Multi-object Fiber Spectroscopic Telescope (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 (dM/sdM/esdM/usdM) 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 7000Å are cleanly measured, which provides accurate spectral typing from late-K to mid-M, and makes it possible to estimate metallicity classes in a way that is more efficient and reliable than with the use of spectral indices or spectral-index based parameters such as ζTiO/CaH. Most of the cool dwarfs observed by LAMOST are found to be metal-rich dwarfs (dM). However, we identify 52 metal-poor M subdwarfs (sdM), 5 very metal-poor extreme subdwarfs (esdM) and 1 probable ultra metal-poor subdwarf (usdM). 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≥-9.8km/s, σU=35.6km/s; <V> =-22.8km/s, σV=30.6km/s; <W> =-7.9km/s, σW=28.4km/s. The resulting values are in 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. Description: The Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST), also named the Guo Shou Jing Telescope, is a quasi-meridian reflecting Schmidt telescope which provides a field of view of up to 20 square degrees. The telescope can produce 4000 spectra in a single exposure, for spectra with a resolution R=1800. A commissioning survey was implemented to test the capabilities of the LAMOST telescope and verify its ability to target and observe 4000 stars at a time. To test the operation in survey mode, six fields (see Table1 in the paper) have been selected at moderately low Galactic latitudes, which provide an abundance of bright targets. The fields are distributed near the Galactic anti-center, with 119°≲gl≲226° and -25°≲gb≲+37°. Each of the field was observed 4-16 times in the course of the commissioning survey, each time targeting a different set of 4000 stars in each field. In this testing phase, however, only about 3500 of the 4000 fibers were available for science targets. In the end, a total of 165219 spectra from science targets were collected from the 48 field exposures. Our templates were assembled from SDSS spectra of relatively bright (r18) late-K and M dwarfs, most drawn from the subset of M dwarfs released in the SDSS DR7, and presented in West et al. 2011 (cat. J/AJ/141/97). Of the 83500 spectra which were passed through the M dwarf classification pipeline (see Section 3), 2612 were positively identified as M dwarfs/subdwarfs by our classification code. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table4.dat 94 2612 M dwarf catalog
See also: V/139 : The SDSS Photometric Catalog, DR 9 (Adelman-McCarthy+, 2012) I/317 : The PPMXL Catalog (Roeser+ 2010) II/294 : The SDSS Photometric Catalog, DR7 (Adelman-McCarthy+, 2009) I/298 : LSPM-North Catalog (Lepine+ 2005) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/AJ/145/102 : Spectroscopy of bright M dwarfs in northern sky (Lepine+, 2013) J/AJ/145/52 : Abundances of late K and M dwarfs in binary stars (Mann+, 2013) J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011) J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011) J/AJ/130/1680 : LSPM-North proper-motion catalog nearby stars (Lepine+, 2005) J/AJ/125/1598 : New high proper motion stars in northern sky (Lepine+, 2003) J/AJ/113/806 : M-Subdwarfs (Gizis 1997) Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 10 F10.6 deg RAdeg Right Ascension (J2000), at Epoch J2000 12- 20 F9.6 deg DEdeg Declination (J2000), at Epoch J2000 21- 27 F7.1 mas/yr pmRA [-147.2/374.5]? Proper motion in RA*cos(DEdeg) 29- 34 F6.1 mas/yr pmDE [-212.7/114.8]? Proper motion in DE 36- 38 I3 mas e_RAdeg [15/133]? Mean error in RAdeg 40- 42 I3 mas e_DEdeg [15/133]? Mean error in DEdeg 44- 47 F4.1 mas/yr e_pmRA [1.2/21.9]? Mean error in pmRA 49- 52 F4.1 mas/yr e_pmDE [1.2/21.9]? Mean error in pmDE 54 A1 --- r_pmDE [LSPT] Source of the proper motion (1) 56- 61 F6.3 mag Jmag [10.8/16.6]? 2MASS J band magnitude (2) 63- 68 F6.3 mag Hmag [9.66/15.92]? 2MASS H band magnitude (2) 70- 75 F6.3 mag Ksmag [9.24/15.44]? 2MASS Ks band magnitude (2) 77- 80 A4 --- Class The "metallicity" class (dK, dM, sdK, sdM, esdK, esdM, usdK, usdM) (3) 82- 89 A8 --- SpT Spectral type (3) 91- 94 I4 pc Dist [29/1458]? Spectroscopic distance (4)
Note (1): The reference codes mean the following: P = Row of the astrometrical parameters are from the PPMXL (Roeser et al. 2010, cat. I/317); S = Row of the astrometrical parameters are from the SUPERBLINK catalog; T = Coordinates parameters are from the 2MASS (cat. II/246); L = Coordinates parameters are from the LAMOST input catalog. Note (2): Magnitude of the counterpart in the 2MASS survey (cat. II/246). 22 M dwarfs do not have 2MASS magnitude because they are too faint to be observed by 2MASS. Note (3): The stars are classified along the dwarf-subdwarf metallicity sequence; the spectral subtype are determined by our template-fitting classification code (see details in Section 3): dK = metal-rich K dwarf; dM = metal-rich M dwarf; sdK = metal-poor K subdwarf; sdM = metal-poor M subdwarf; esdK = metal-poor extreme K subdwarf; esdM = metal-poor extreme M subdwarf; usdK = ultra metal-poor K subdwarf; usdM = ultra metal-poor M subdwarf. Note (4): Based on the absolute infrared J band magnitude to the spectral subtype relationship. The estimated uncertainties are about 40%.
History: From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 05-Oct-2015
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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