J/ApJ/858/L7    Red clump stars selected from LAMOST and APOGEE    (Ting+, 2018)

A large and pristine sample of standard candles across the Milky Way: ∼100,000 red clump stars with 3% contamination. Ting Y.-S., Hawkins K., Rix H.-W. <Astrophys. J., 858, L7 (2018)> =2018ApJ...858L...7T 2018ApJ...858L...7T
ADC_Keywords: Asteroseismology; Abundances, [Fe/H]; Spectroscopy Keywords: methods: data analysis ; stars: distances ; techniques: spectroscopic Abstract: Core helium-burning red clump (RC) stars are excellent standard candles in the Milky Way. These stars may have more precise distance estimates from spectrophotometry than from Gaia parallaxes beyond 3kpc. However, RC stars have values of Teff and logg that are very similar to some red giant branch (RGB) stars. Especially for low-resolution spectroscopic studies where Teff, logg, and [Fe/H] can only be estimated with limited precision, separating RC stars from RGB through established methods can incur ∼20% contamination. Recently, Hawkins+ (2018ApJ...853...20H 2018ApJ...853...20H) demonstrated that the additional information in single-epoch spectra, such as the C/N ratio, can be exploited to cleanly differentiate RC and RGB stars. In this second paper of the series, we establish a data-driven mapping from spectral flux space to independently determined asteroseismic parameters, the frequency and the period spacing. From this, we identify 210371 RC stars from the publicly available LAMOST DR3 and APOGEE DR14 data, with ∼9% of contamination. We provide an RC sample of 92249 stars with a contamination of only ∼3%, by restricting the combined analysis to LAMOST stars with S/Npix≥75. This demonstrates that high-signal-to-noise ratio (S/N), low-resolution spectra covering a broad wavelength range can identify RC samples at least as pristine as their high- resolution counterparts. As coming and ongoing surveys such as TESS, DESI, and LAMOST will continue to improve the overlapping training spectroscopic-asteroseismic sample, the method presented in this study provides an efficient and straightforward way to derive a vast yet pristine sample of RC stars to reveal the three-dimensional (3D) structure of the Milky Way. Description: In this paper, we set out to establish data-driven mapping from spectra to asteroseismic parameters, using an extensive sample of stars with asteroseismology from Kepler and spectra from APOGEE (Majewski+ 2017AJ....154...94M 2017AJ....154...94M) and LAMOST (Xiang+ 2017MNRAS.467.1890X 2017MNRAS.467.1890X). The spectra serve as input to predict the asteroseismic parameters as output. Once such a mapping is optimized, it can then be applied to all spectra to predict their asteroseismic values from such spectra. We applied this approach to two large-scale spectroscopic surveys that span different resolutions and wavelength coverage as a sample application of this method. We adopted the high-resolution (R=22500) infrared (λ=1500-1700nm) APOGEE survey and the low-resolution (R=1800) optical (λ=390-900nm) LAMOST survey. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 86 347727 Asteroseismic parameters added catalogs for LAMOST; from erratum published in 2018, ApJL, 864, 39 table2.dat 86 80944 Asteroseismic parameters added catalogs for APOGEE -------------------------------------------------------------------------------- See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) V/133 : Kepler Input Catalog (Kepler Mission Team, 2009) III/284 : APOGEE-2 data from DR16 (Majewski+, 2017) V/153 : LAMOST DR4 catalogs (Luo+, 2018) J/ApJ/808/16 : Cannon: a new approach to determine abundances (Ness+, 2015) J/ApJS/220/19 : LAMOST obs. in the Kepler field. I. (De Cat+, 2015) J/A+A/588/A87 : Seismic global parameters of 6111 KIC (Vrard+, 2016) J/A+A/594/A43 : APOGEE/Kepler sample stars abundances (Hawkins+, 2016) J/AJ/152/6 : Kepler star parameters with LAMOST + seismic data (Wang+, 2016) J/ApJ/836/5 : Abundances of LAMOST giants from APOGEE DR12 (Ho+, 2017) J/AJ/155/68 : Elemental abundances of KOIs in APOGEE. I. (Wilson+, 2018) J/AJ/156/18 : APOGEE DR14:Binary companions of evolved stars (Price-Whelan+, 2018) J/AJ/156/84 : APOGEE-2 survey of Orion Complex. II. (Kounkel+, 2018) J/MNRAS/476/2117 : Outliers and similarity in APOGEE (Reis+, 2018) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 A19 --- ID Identifier (JHHMMSS.ss+DDMMSS.s) 21- 29 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) 31- 38 F8.5 deg DEdeg Declination in decimal degrees (J2000) 40- 45 F6.1 --- S/N [0/1212] Median Signal-to-Noise per pixel 47- 52 F6.2 s DeltaP [29/410] Period spacing (1) 54- 58 F5.2 uHz Deltanu [1.7/17.5] Frequency separation (2) 60- 70 A11 --- Class Classification (3) 72- 75 I4 K Teff [4300/5388] Effective temperature (4) 77- 80 F4.2 [cm/s2] log(g) [1/3.5] log surface gravity (4) 82- 86 F5.2 [Sun] [Fe/H] [-2.4/0.5] Metallicity (4) -------------------------------------------------------------------------------- Note (1): Of the mixed g and p modes. Note (2): Between adjacent acoustic p-modes. Note (3): For LAMOST, we further distinguish red clump (RC) stars with S/Npix>75 to be "RC_Pristine", and RC stars with S/Npix<75 to be "RC". Stars that have DeltaP>250s are classified as RC stars. Note (4): Adopted from LAMOST DR3. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 18 A18 --- ID Identifier (2MHHMMSSss+DDMMSSs or APHHMMSSss+DDMMSSs) 20- 28 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000) 30- 38 F9.5 deg DEdeg Declination in decimal degrees (J2000) 40- 45 F6.1 --- S/N [24/2204] Median Signal-to-Noise per pixel 47- 52 F6.2 s DeltaP [25/393] Period spacing (1) 54- 58 F5.2 uHz Deltanu [2/17.4] Frequency separation (2) 60- 70 A11 --- Class Classification (3) 72- 75 I4 K Teff [4418/5226] Effective temperature (4) 77- 80 F4.2 [cm/s2] log(g) [2/3.4] log surface gravity (4) 82- 86 F5.2 [Sun] [Fe/H] [-2.6/0.5] Metallicity (4) -------------------------------------------------------------------------------- Note (1): Of the mixed g and p modes. Note (2): Between adjacent acoustic p-modes. Note (3): For APOGEE, since most stars have S/Npix>75, we assume all red clump (RC) stars to be "RC_Pristine". Stars that have DeltaP>250s are classified as RC stars. Note (4): Adopted from APOGEE DR14. -------------------------------------------------------------------------------- History: From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Apr-2019
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