J/AJ/153/261 Red giant stellar parameters in the LMC bar (Song+, 2017)
An expanded chemo-dynamical sample of red giants in the bar of the Large
Magellanic Cloud.
Song Y.-Y., Mateo M., Walker M.G., Roederer I.U.
<Astron. J., 153, 261 (2017)>
=2017AJ....153..261S 2017AJ....153..261S
ADC_Keywords: Magellanic Clouds; Stars, giant; Abundances, [Fe/H];
Photometry; Optical
Keywords: galaxies: kinematics and dynamics ; galaxies: stellar content ;
Magellanic Clouds ; stars: abundances ;
stars: fundamental parameters ; techniques: spectroscopic
Abstract:
We report new spectroscopic observations obtained with the
Michigan/Magellan Fiber System of 308 red giants (RGs) located in two
fields near the photometric center of the bar of the Large Magellanic
Cloud. This sample consists of 131 stars observed in previous studies
(in one field) and 177 newly observed stars (in the second field)
selected specifically to more reliably establish the metallicity and
age distributions of the bar. For each star, we measure its
heliocentric line-of-sight velocity, surface gravity, and metallicity
from its high-resolution spectrum (effective temperatures come from
photometric colors). The spectroscopic Hertzsprung-Russell diagrams-
modulo small offsets in surface gravities-reveal good agreement with
model isochrones. The mean metallicity of the 177-RG sample is
[Fe/H]=-0.76±0.02 with a metallicity dispersion σ=0.28±0.03.
The corresponding metallicity distribution-corrected for selection
effects-is well fitted by two Gaussian components: one metal-rich with
a mean -0.66±0.02 and a standard deviation 0.17±0.01, and the
other metal-poor with -1.20±0.24 and 0.41±0.06. The metal-rich and
metal-poor populations contain approximately 85% and 15% of stars,
respectively. We also confirm that the velocity dispersion in the bar
center decreases significantly from 31.2±4.3 to 18.7±1.9km/s with
increasing metallicity over the range -2.09 to -0.38. Individual
stellar masses are estimated using the spectroscopic surface gravities
and the known luminosities. We find that lower mass, hence older, RGs
have larger metallicity dispersion and lower mean metallicity than the
higher-mass, younger RGs. The estimated masses, however, extend to
implausibly low values (∼0.1M☉), making it impossible to obtain
an absolute age-metallicity or age distribution of the bar.
Description:
The high-resolution spectra were obtained with the Michigan/Magellan
Fiber System (M2FS) on the Magellan/Clay Telescope over two separate
fields that both are near the photometric center of the LMC bar:
"LMCC" (Cole+ J/AJ/129/1465) at RAJ2000=05:24:35.96,DEJ2000=-69:50:09.4,
observed on 2015 Nov 15 and
"LMC1" at RAJ2000=05:22:11.09,DEJ2000=-69:45:52.3, observed on 2014
Dec 23 and 2015 Nov 18.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 76 331 Sample selected in the LMC bar
table4.dat 54 312 *Stellar parameters of the sample in the LMC bar
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Note on table4.dat: We list only results for spectra with median SNR per pixel
greater than 5 (SNR>5), which results in 133 (out of 147 observed) targets in
LMCC and 179 (out of 184) in LMC1. Excluding double/blended stars
(see Section 4.1), the final LMCC and LMC1 sample sizes are 131 and 177,
respectively.
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See also:
J/AJ/117/238 : LMC extended catalog (Bica+, 1999)
J/AJ/120/1808 : Stroemgren photometry in LMC disk (Cole+, 2000)
J/A+AS/141/371 : Low-mass stars evolutionary tracks (Girardi+, 2000)
J/AcA/50/307 : OGLE LMC BVI photometry (Udalski+, 2000)
J/MNRAS/339/701 : Velocities and BR photometry in LMC (Zhao+, 2003)
J/A+A/421/937 : Metal abundances of LMC RR Lyrae (Gratton+, 2004)
J/AJ/129/1465 : Spectroscopy of red giants in the LMC bar (Cole+, 2005)
J/AJ/135/836 : Calcium triplet index in LMC stars (Carrera+, 2008)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/A+A/480/379 : Abundances of 59 red giants in LMC (Pompeia+, 2008)
J/AJ/136/375 : Chemical composition of LMC red giants (Mucciarelli+, 2008)
J/MNRAS/405/1770 : LMC red giants in E sequence (Nicholls+, 2010)
J/AJ/142/61 : RGB stars in LMC outer disk (Carrera+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/761/33 : Chemical properties of stars in the LMC disk (Lapenna+, 2012)
J/A+A/560/A44 : Abundances of LMC bar & disk stars (Van der Swaelmen+, 2013)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/808/108 : M2FS stellar spectroscopy of Reticulum 2 (Walker+, 2015)
J/MNRAS/448/2717 : Bayesian analysis of stellar spectra (Walker+, 2015)
J/ApJ/817/40 : High-resolution NIR spectra of local giants (Feuillet+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Identifier, Field-Fiber (G1)
11- 12 I2 h RAh [5] Hour of Right Ascension (J2000)
14- 15 I2 min RAm [19/26] Minute of Right Ascension (J2000)
17- 21 F5.2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- [-] Sign of the Declination (J2000)
24- 25 I2 deg DEd [69/70] Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of Declination (J2000)
35- 40 F6.3 mag Vmag [16.5/18.5] V band magnitude (1)
42- 46 F5.3 mag e_Vmag [0.003/0.1] Uncertainty in Vmag
48- 53 F6.3 mag Imag [15.2/17] I band magnitude (1)
55- 59 F5.3 mag e_Imag [0.003/0.1] Uncertainty in Imag
61- 76 A16 --- OName Other identifier (2)
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Note (1): V- and I-band photometry from the OGLE-II catalog
(Udalski+ J/AcA/50/307) for stars in LMC1. The LMCC targets were
selected from the transformed CTIO photometry according to C05
(Cole+ J/AJ/129/1465).
Note (2): The other identifiers are the 2MASS identifier
(<2MASS JHHMMSSss+DDMMSSs> in Simbad) for LMCC targets;
OGLE-II ID ( in Simbad) for LMC1 targets.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ID Identifier, Field-Fiber (G1)
11- 14 F4.1 --- SN [5/25] Signal-to-noise
16- 20 F5.1 km/s vlos [175/344] Line-of-sight velocity
22- 24 F3.1 km/s e_vlos [0.3/1] Uncertainty in vlos
26- 29 I4 K Teff [4003/5199] Stellar effective temperature
31- 33 I3 K e_Teff [57/247] Uncertainty in Teff
35- 38 F4.2 [cm/s2] logg [0.07/3.3] Stellar surface gravity, log
40- 43 F4.2 [cm/s2] e_logg [0.06/0.5] Uncertainty in logg
45- 49 F5.2 [-] [Fe/H] [-2.5/-0.3] Metallicity
51- 54 F4.2 [-] e_[Fe/H] [0.04/0.2] Uncertainty in [Fe/H]
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Global notes:
Note (G1): The Identifier is comprised of the field name (LMCC or LMC1
-- see the "Description" section above) and the science fiber number.
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History:
From electronic version of the journal (MRT tables sent directly by AAS)
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 08-Mar-2019