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 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 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 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 2010ApJ...721L..92R ; 2011ApJ...737....9R 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 1973AJ.....78..687B, Cat. III/46)
weak-metal candidates studied by Norris et al. (1985ApJS...58..463N 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:
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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
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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
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Bytes Format Units Label Explanations
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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 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
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Byte-by-byte Description of file: table2.dat
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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)
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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 1985ApJS...58..463N) and that assigned based on the atmospheric
parameters determined by the n-SSPP.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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)
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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);
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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
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Byte-by-byte Description of file: table5.dat
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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)
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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.
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History:
From electronic version of the journal
References:
Norris et al., Paper I, 1985ApJS...58..463N 1985ApJS...58..463N
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 26-Apr-2017