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J/ApJ/794/58   Metal-poor stars in the thick disk of the Galaxy   (Beers+, 2014)

Population studies. XIII. A new analysis of the Bidelman-MacConnell "weak-metal" stars - Confirmation of metal-poor stars in the thick disk of the Galaxy. Beers T.C., Norris J.E., Placco V.M., Lee Y.S., Rossi S., Carollo D., Masseron T. <Astrophys. J., 794, 58 (2014)> =2014ApJ...794...58B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, population II ; Abundances ; Photometry ; Reddening ; Radial velocities ; Spectroscopy ; Space velocities Parallaxes, trigonometric ; Stars, distances ; Proper motions Keywords: Galaxy: kinematics and dynamics - Galaxy: stellar content - Galaxy: structure - stars: abundances - stars: Population II Abstract: A new set of very high signal-to-noise (S/N>100/1), medium-resolution (R∼3000) optical spectra have been obtained for 302 of the candidate "weak-metal" stars selected by Bidelman & MacConnell (1973AJ.....78..687B, Cat. III/46). We use these data to calibrate the recently developed generalization of the Sloan Extension for Galactic Exploration and Understanding and Exploration (SEGUE) Stellar Parameter Pipeline, and obtain estimates of the atmospheric parameters (Teff, log g, and [Fe/H]) for these non-Sloan Digital Sky Survey/SEGUE data; we also obtain estimates of [C/Fe]. The new abundance measurements are shown to be consistent with available high-resolution spectroscopic determinations, and represent a substantial improvement over the accuracies obtained from the previous photometric estimates reported in Paper I of this series (Norris et al. 1985ApJS...58..463N). The apparent offset in the photometric abundances of the giants in this sample noted by several authors is confirmed by our new spectroscopy; no such effect is found for the dwarfs. The presence of a metal-weak thick-disk (MWTD) population is clearly supported by these new abundance data. Some 25% of the stars with metallicities -1.8<[Fe/H]≤-0.8 exhibit orbital eccentricities e<0.4, yet are clearly separated from members of the inner-halo population with similar metallicities by their location in a Lindblad energy versus angular momentum diagram. A comparison is made with recent results for a similar-size sample of Radial Velocity Experiment stars from Ruchti et al. (2010ApJ...721L..92R ; 2011ApJ...737....9R). We conclude, based on both of these samples, that the MWTD is real, and must be accounted for in discussions of the formation and evolution of the disk system of the Milky Way. Description: During several observing runs conducted in 1996 January, 1996 December, and 1997 June, optical spectra for a total of 302 stars from the subsample of 309 Bidelman & Maconnell (1973AJ.....78..687B, Cat. III/46) weak-metal candidates studied by Norris et al. (1985ApJS...58..463N) (hereafter referred to as the B&M sample) were obtained with the Siding Spring Observatory (SSO) 2.3 m telescope, using the Double Beam Spectrograph. These spectra covered the wavelength interval 3800Å≤λ≤4500Å, with a resolving power of R∼3000, similar to that obtained during the course of previous work on follow-up spectroscopy by Norris et al. (1999, J/ApJS/123/639) of metal-poor candidates selected from the HK survey of Beers et al. (1985, J/AJ/90/2089; 1992, J/AJ/103/1987). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 71 302 Photometric Information and Adopted Reddening table2.dat 113 302 Radial Velocities, Line Indices, Atmospheric Parameters, and Type Assignments table3.dat 35 302 Carbon Abundance Ratio Estimates table4.dat 98 302 Parallaxes, Distance Estimates, and Proper Motions table5.dat 82 302 Space Motions and Orbital Parameters
See also: J/AJ/90/2089 : Stars of very low metal abundance. I (Beers+, 1985) J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992) J/ApJS/123/639 : UBV photometry of metal-weak candidates (Norris+, 1999) J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [BM-] 4- 6 I3 --- BM [001/326] BM identifier (BM-NNN) 8- 18 A11 --- Name Common star name 20- 24 F5.1 deg GLON Galactic longitude 26- 30 F5.1 deg GLAT Galactic latitude 32- 36 F5.2 mag Vmag ? Adopted V band magnitude 38- 41 F4.2 mag B-V ? Adopted (B-V) color 43- 47 F5.3 mag Jmag ? 2MASS J band magnitude 49- 53 F5.3 mag J-K ? 2MASS (J-K) color 55- 60 F6.3 mag E(B-V)S Schlegel et al. 1998 reddening estimate (1998ApJ...500..525S) 62- 66 F5.2 mag E(B-V)A Adopted reddening estimate 68- 71 F4.2 mag E(B-V)F Final estimated reddening
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [BM-] 4- 6 I3 --- BM [001/326] BM identifier (BM-NNN) 8 I1 --- N [1/5] Number of measurements 10- 13 I4 km/s RVM Radial velocity from medium-resolution spectra 15- 18 I4 km/s RVH ? Radial velocity from high-resolution spectra 20- 24 F5.2 0.1nm KP KP index; Ca II K line strength (1) 26- 29 F4.2 0.1nm HP2 ? HP2 index; Hδ line strength (1) 31- 34 F4.2 0.1nm GP GP index; CH G-band strength (1) 36- 39 F4.2 0.1nm HG2 ? HG2 index; Hγ line strength (1) 41- 46 F6.3 [-] LACF Log AutoCorrelation Function index 48- 51 I4 K TeffS ? n-SSPP derived effective temperature 53- 56 F4.2 [cm/s2] log(g)S ? n-SSPP derived log surface gravity 58- 62 F5.2 [-] [Fe/H]S ? n-SSPP derived metallicity 64- 67 I4 K TeffH ? High-resolution derived effective temperature 69- 72 F4.2 [cm/s2] log(g)H ? High-resolution derived log surface gravity 74- 78 F5.2 [-] [Fe/H]H ? High-resolution derived metallicity 80- 83 I4 K TeffC ? Corrected n-SSPP derived effective temperature 85- 89 F5.2 [cm/s2] log(g)C ? Corrected n-SSPP derived log surface gravity 91- 95 F5.2 [-] [Fe/H]C ? Corrected n-SSPP derived metallicity 97-101 F5.2 [-] [Fe/H]N ? DDO photometry-based metallicity 103-113 A11 --- Type Luminosity type (2)
Note (1): In units of Angstroms. Note (2): In the form N/S, where "N" indicates those assigned by NBP, while "S" indicates the classes assigned by the n-SSPP. A ":" appended indicates a disagreement between the type assignment (based on photometry) in Paper I (Norris et al. 1985ApJS...58..463N) and that assigned based on the atmospheric parameters determined by the n-SSPP.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [BM-] 4- 6 I3 --- BM [001/326] BM identifier (BM-NNN) 8- 12 F5.2 [-] [C/Fe]S ? Medium-resolution carbonicity estimate 14- 15 A2 --- DETECT [DLUN: ] Detection code (1) 17- 21 F5.3 --- CC ? Correlation coefficient (2) 23- 27 F5.2 [-] [C/Fe]H ? High-resolution carbonicity estimate 29- 33 F5.2 [-] [C/Fe]C ? Corrected n-SSPP carbonicity estimate 35 A1 --- f_[C/Fe]C [a] Flag on [C/Fe]C (3)
Note (1): Code as follows: D = detection; L = lower limit; U = upper limit; N = not analyzed. Note (2): Obtained between the observed spectrum and the best-matching [C/Fe] from the model grids. Note (3): Flag as follows: a = CEMP star ([C/Fe]C≥+0.7, DETECT="D", and CC≥0.7);
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [BM-] 4- 6 I3 --- BM [001/326] BM identifier (BM-NNN) 8- 12 F5.2 mas plxHIP ? HIPPARCOS parallax 14- 18 F5.2 mas e_plxHIP ? Error in plxHIP 20- 24 F5.3 kpc Dpho ? Photometric distance 26- 32 F7.3 kpc DHIP ? Trigonometric distance 34- 39 F6.2 --- Ratio ? Ratio of HIPPARCOS error to its parallax 41- 45 F5.3 kpc Dado ? Adopted distance 47- 52 F6.3 kpc e_Dado ? Error in Dado 54- 61 F8.2 mas/yr pmRA Proper motion along Right Ascension 63- 70 F8.2 mas/yr pmDE Proper motion along Declination 72- 76 F5.2 mas/yr e_pmRA Error in pmRA 78- 82 F5.2 mas/yr e_pmDE Error in pmDE 84- 98 A15 --- ID HIPPARCOS or TYCHO identifier
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 3 A3 --- --- [BM-] 4- 6 I3 --- BM [001/326] BM identifier (BM-NNN) 8- 13 F6.3 kpc R Distance from Galactic center 15- 20 F6.3 kpc Z Distance above Galactic plane 22- 25 I4 km/s U ? The U velocity 27- 30 I4 km/s V The V velocity 32- 35 I4 km/s W The W velocity 37- 38 I2 km/s e_U Error in U 40- 41 I2 km/s e_V Error in V 43- 44 I2 km/s e_W Error in W 46- 49 I4 km/s VR Velocity projected onto Galactic plane (1) 51- 54 I4 km/s Vphi Derived rotation velocity 56- 59 F4.2 kpc rperi ? Perigalactic radius 61- 65 F5.2 kpc rapo ? Apogalactic radius 67- 71 F5.2 kpc Zmax ? Maximum Galactic scale height 73- 76 F4.2 --- ecc ? Orbital eccentricity 78- 82 A5 --- INOUT Membership code (2)
Note (1): Positive in the direction away from the Galactic center. Note (2): Indicates membership in various subsamples considered in this paper (see text). The first digit : 1 = if the star is accepted for the kinematic analysis; 0 = if not. The second digit : 1 = if the star is likely to be a member of the disk system, according to the Lindblad diagram shown in Figure 12; 0 = if not. The third digit : 1 = if the star is a likely disk member with metallicity in the range -0.8<[Fe/H]≤-0.5; 2 = if it is a likely disk member in the metallicity range -1.8<[Fe/H]≤-0.8; 0 = if not.
History: From electronic version of the journal References: Norris et al., Paper I, 1985ApJS...58..463N
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 26-Apr-2017
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