J/AJ/155/256 Spectroscopic validation of RAVE metal-poor stars (Placco+, 2018)
Spectroscopic validation of low-metallicity stars from RAVE.
Placco V.M., Beers T.C., Santucci R.M., Chaname J., Sepulveda M.P.,
Coronado J., Points S.D., Kaleida C.C., Rossi S., Kordopatis G., Lee Y.S.,
Matijevic G., Frebel A., Hansen T.T., Holmbeck E.M., Rasmussen K.C.,
Roederer I.U., Sakari C.M., Whitten D.D.
<Astron. J., 155, 256-256 (2018)>
=2018AJ....155..256P 2018AJ....155..256P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, halo ; Stars, carbon ; Stars, metal-deficient ;
Spectroscopy ; Radial velocities ; Effective temperatures ;
Abundances ; Proper motions ; Parallaxes, trigonometric
Keywords: Galaxy: halo - stars: abundances - stars: atmospheres -
stars: carbon - stars: Population II -
techniques: imaging spectroscopy
Abstract:
We present results from a medium-resolution (R∼2000) spectroscopic
follow-up campaign of 1694 bright (V<13.5), very metal-poor star candidates
from the RAdial Velocity Experiment (RAVE). Initial selection of the
low-metallicity targets was based on the stellar parameters published
in RAVE Data Releases 4 (Cat. III/272) and 5 (Cat. III/279). Follow up was
accomplished with the Gemini-N and Gemini-S, the ESO/NTT, the KPNO/Mayall,
and the SOAR telescopes. The wavelength coverage for most of the observed
spectra allows for the determination of carbon and α-element
abundances, which are crucial for considering the nature and frequency
of the carbon-enhanced metal-poor (CEMP) stars in this sample. We find
that 88% of the observed stars have [Fe/H]=< -1.0, 61% have [Fe/H]=< -2.0,
and 3% have [Fe/H]=< -3.0 (with four stars at [Fe/H]=< -3.5). There are
306 CEMP star candidates in this sample, and we identify 169 CEMP Group I,
131 CEMP Group II, and 6 CEMP Group III stars from the A(C) versus [Fe/H]
diagram. Inspection of the [α/C] abundance ratios reveals that five
of the CEMP Group II stars can be classified as "mono-enriched
second-generation" stars. Gaia DR1 matches were found for 734 stars, and
we show that transverse velocities can be used as a confirmatory selection
criteria for low-metallicity candidates. Selected stars from our validated
list are being followed-up with high-resolution spectroscopy to reveal
their full chemical-abundance patterns for further studies.
Description:
The low-metallicity candidates were selected from the RAVE DR4
(Kordopatis et al. 2013, Cat. III/272) and DR5 (Kunder et al. 2017,
Cat. III/279) catalogs.
The medium-resolution spectroscopic follow-up campaign was conducted
from semesters 2014A to 2017A and collected 1835 spectra of 1694 unique
metal-poor candidates. We used six different telescope/instrument setups:
(i) SOAR/Goodman, (ii) Gemini North/GMOS-N, (iii) Gemini South/GMOS-S,
(iv) Mayall/RCSPEC, (v) Mayall/KOSMOS, and (vi) NTT/EFOSC-2.
The stellar atmospheric parameters, as well as carbon and α-element
abundances, were determined using the n-SSPP (Beers et al. 2014,
J/ApJ/794/58; 2017, J/ApJ/835/81), a modified version of the SEGUE Stellar
Parameter Pipeline (SSPP; Lee et al. 2008AJ....136.2022L 2008AJ....136.2022L; 2008,
J/AJ/136/2050; 2013AJ....146..132L 2013AJ....146..132L).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 64 1694 Observing details
table2.dat 90 1694 Coordinates, magnitudes, color indices,
and redenning estimates
table3.dat 128 1694 *Stellar parameters from RAVE DR4, RAVE DR5,
RAVE-on, and the n-SSPP
table4.dat 108 734 Gaia/TGAS parameters
table5.dat 54 306 Group assignments for carbon-enhanced metal-poor
(CEMP) stars
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Note on table3.dat:
RAVE DR4 = Kordopatis et al. 2013, Cat. III/272;
RAVE DR5 = Kunder et al. 2017, Cat. III/279;
RAVE-on = Casey et al. 2017ApJ...840...59C 2017ApJ...840...59C;
n-SSPP = Beers et al. 2014, J/ApJ/794/58; 2017, J/ApJ/835/81.
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See also:
III/272 : RAVE 4th data release (Kordopatis+, 2013)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
III/279 : RAVE 5th data release (Kunder+, 2017)
J/ApJ/658/367 : Abundances of carbon stars in Galactic halo (Komiya+, 2007)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/ApJ/737/9 : RAVE spectroscopic data of stars in the thick disk
(Ruchti+, 2011)
J/ApJ/762/26 : Most metal-poor stars. II. 190 Galactic halo stars
(Yong+, 2013)
J/ApJ/794/58 : Metal-poor stars in the thick disk of the Galaxy (Beers+, 2014)
J/ApJ/833/20 : Carbon-enhanced metal-poor (CEMP) star abundances (Yoon+, 2016)
J/ApJ/833/119 : Distances of Gaia DR1 TGAS sources (Astraatmadja+, 2016)
J/ApJ/835/81 : Bright metal-poor stars from HES Survey. II. (Beers+, 2017)
J/ApJ/847/16 : NLTE spectroscopy. II. Galactic metal-poor stars
(Bergemann+, 2017)
J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- RAVE RAVE positional identifier (JHHMMSS.s+DDMMSS)
18- 27 A10 "date" Date UTC observation date
29- 36 A8 --- Tel Telescope
38- 44 A7 --- Inst Instrument
46- 59 A14 --- ID Proposal identifier
61- 64 I4 s Exp [3/1500] Exposure time
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- RAVE RAVE positional identifier (JHHMMSS.s+DDMMSS)
18- 19 I2 h RAh Hour of Right Ascension (J2000)
21- 22 I2 min RAm Minute of Right Ascension (J2000)
24- 28 F5.2 s RAs Second of Right Ascension (J2000)
30 A1 --- DE- Sign of the Declination (J2000)
31- 32 I2 deg DEd Degree of Declination (J2000)
34- 35 I2 arcmin DEm Arcminute of Declination (J2000)
37- 40 F4.1 arcsec DEs Arcsecond of Declination (J2000)
42- 48 F7.3 deg GLON [0.06/359.348] Galactic longitude
50- 56 F7.3 deg GLAT [-85.786/65.804] Galactic latitude
58- 63 F6.3 mag Vmag [7.278/15.59]? APASS V band magnitude
(Henden & Munari 2014CoSka..43..518H 2014CoSka..43..518H)
65- 70 F6.3 mag B-V [-0.128/4.277]? APASS B-V color (Henden & Munari
2014CoSka..43..518H 2014CoSka..43..518H)
72- 77 F6.3 mag Jmag [3.414/12.975] 2MASS J band magnitude
79- 84 F6.3 mag J-Ks [-0.102/2.704] 2MASS J-Ks color
86- 90 F5.3 mag E(B-V) [0.003/0.3] Reddening estimate (Schlegel et al.
1998ApJ...500..525S 1998ApJ...500..525S)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- RAVE RAVE positional identifier
(JHHMMSS.s+DDMMSS)
18- 24 F7.2 km/s RV-DR4 [-983.66/989.55]? Radial velocity from
RAVE DR4
26- 29 I4 K Teff-DR4 [3000/8000]? Stellar effective temperature
from RAVE DR4
31- 34 F4.2 [cm/s2] logg-DR4 [0.01/5.5]? Stellar surface gravity from
RAVE DR4
36- 40 F5.2 --- [Fe/H]-DR4 [-5.29/0.26]? Metallicity from RAVE DR4
42- 48 F7.2 km/s RV-DR5 [-983.66/989.55]? Radial velocity from
RAVE DR5
50- 53 I4 K Teff-DR5 [3086/7881]? Stellar effective temperature
from RAVE DR5
55- 58 I4 K Teff-DR5-IR [3485/9503]? Stellar effective temperature
from IR flux method, from RAVE DR5
60- 63 F4.2 [cm/s2] logg-DR5 [0.52/5.18]? Stellar surface gravity from
RAVE DR5
65- 69 F5.2 --- [Fe/H]-DR5 [-9.9/0.49]? Metallicity from RAVE DR5
71- 77 F7.2 km/s RV-on [-983.66/989.55]? Radial velocity from
RAVE-on
79- 82 I4 K Teff-on [3579/7701]? Stellar effective temperature
from RAVE-on
84- 88 F5.2 [cm/s2] logg-on [-0.22/4.96]? Stellar surface gravity from
RAVE-on
90- 94 F5.2 --- [Fe/H]-on [-3.88/0.56]? Metallicity from RAVE-on
96- 99 I4 K Teff [4027/9627]? Stellar effective temperature
from this work
101-104 F4.2 [cm/s2] logg [0.12/4.85]? Stellar surface gravity from
this work
106-110 F5.2 --- [Fe/H] [-3.74/0.32]? Metallicity from this work
112-116 F5.2 --- [C/Fe] [-1.59/2.49]? Carbon-abundance ratio from
this work
118-122 F5.2 --- D[C/Fe] [0/0.77]? Differential carbon-abundance
(Placco et al. 2014ApJ...797...21P 2014ApJ...797...21P)
124-128 F5.2 --- [a/Fe] [-0.2/0.6]? α-element abundance ratio
from this work
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- RAVE RAVE positional identifier (JHHMMSS.s+DDMMSS)
18- 36 I19 --- TGAS Gaia/TGAS identifier (Cat. I/337)
38- 42 F5.2 mag Gmag [6.28/12.45] Gaia/TGAS G magnitude
44- 51 F8.3 mas/yr pmRA [-271.336/286.579] Gaia/TGAS proper motion in
right ascension direction
53- 57 F5.3 mas/yr e_pmRA [0.034/7.464] Uncertainty in pmRA
59- 66 F8.3 mas/yr pmDE [-283.56/103.268] Gaia/TGAS proper motion in
declination direction
68- 72 F5.3 mas/yr e_pmDE [0.024/8.203] Uncertainty in pmDE
74- 79 F6.3 mas Plx [-2.63/18.07] Gaia/TGAS parallax π
81- 85 F5.3 mas e_Plx [0.21/0.99] Uncertainty in Plx
87- 91 F5.3 kpc Dist [0.055/3.11] Derived distance (1)
93- 97 F5.3 kpc e_Dist [0.001/3.231] Uncertainty in Dist (1)
99-101 I3 km/s Vt [1/533] Transverse velocity
103-108 F6.3 kpc Z [-2.987/2.314] Height above Galactic plane
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Note (1): Distances and errors infered from the Milky Way prior were taken
from the Astraatmadja & Bailer-Jones (2016, J/ApJ/833/119) catalog.
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- RAVE RAVE positional identifier (JHHMMSS.s+DDMMSS)
18- 22 F5.2 mag Vmag [9.04/13.79]? APASS V band magnitude
(Henden & Munari 2014CoSka..43..518H 2014CoSka..43..518H)
24- 27 I4 K Teff [4153/7766] Stellar effective temperature
29- 33 F5.2 --- [Fe/H] [-3.68/-1.02] Metallicity
35- 39 F5.2 --- [C/Fe] [-0.01/2.49] Carbon-abundance ratio
41- 45 F5.2 --- [C/Fe]c [0.7/2.62] Corrected carbon-abundance ratio
47- 50 F4.2 --- A(C)c [6.06/9.32] Corrected absolute carbon abundance
52- 54 A3 --- Group [I II III] Carbon-enhanced metal-poor group (1)
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Note (1): The CEMP stars identified in this work can be further sub-classified,
based on their position in the Yoon-Beers A(C) versus [Fe/H] diagram,
following Yoon et al. (2016, J/ApJ/833/20). Roughly, one would expect to find
(assuming [Fe/H]=< -1.0 and [C/Fe]>=+0.7):
Group I = CEMP-s (or CEMP-i) stars for -3.5~<[Fe/H]~< -2.5 and A(C)>∼7.25 or
[Fe/H]≳ -2.5;
Group II = CEMP-no stars for [Fe/H]~< -2.5, A(C)~<7.25, and [C/Fe]=<+1.5;
Group III = CEMP-no stars for [Fe/H]~< -2.5, A(C)~<7.25, and [C/Fe]>+1.5.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 07-Jan-2019