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 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: =-9.8km/s,
σU=35.6km/s; =-22.8km/s, σV=30.6km/s; =-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