J/AJ/135/836 Calcium triplet index in LMC stars (Carrera+, 2008)
The chemical enrichment history of the Large Magellanic Cloud.
Carrera R., Gallart C., Hardy E., Aparicio A., Zinn R.
<Astron. J., 135, 836-849 (2008)>
=2008AJ....135..836C 2008AJ....135..836C
ADC_Keywords: Stars, giant ; Magellanic Clouds ; Spectra, infrared ;
Radial velocities ; Photometry, VRI
Keywords: galaxies: abundances - galaxies: evolution - Magellanic Clouds -
galaxies: stellar content
Abstract:
Infrared CaII triplet (CaT) spectroscopy has been used to derive stellar
metallicities for individual stars in four Large Magellanic Cloud
fields situated at galactocentric distances of 3°, 5°, 6°,
and 8° to the north of the bar. The combination of spectroscopy
with deep CCD photometry has allowed us to break the RGB
age-metallicity degeneracy and compute the ages for the objects
observed spectroscopically. The obtained age-metallicity relationships
(AMRs) for our four fields are statistically indistinguishable. We
conclude that the lower mean metallicity in the outermost field is a
consequence of it having a lower fraction of intermediate-age stars,
which are more metal-rich than the older stars. The disk AMR is
similar to that for clusters. However, the lack of objects with ages
between 3 and 10Gyr is not observed in the field population. Finally,
we used data from the literature to derive consistently the AMR of the
bar. Simple chemical evolution models have been used to reproduce the
observed AMRs with the purpose of investigating which mechanism has
participated in the evolution of the disk and bar.
Description:
The observations were carried out in two different runs, in 2002
December and in 2005 January, at the CTIO 4m telescope with the HYDRA
multifiber spectrograph.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 635 LMC RGB stars observed
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See also:
J/A+A/480/379 : Abundances of 59 red giants in LMC (Pompeia+, 2008)
J/AJ/134/1298 : CaII equivalent widths in 29 Galactic clusters (Carrera+, 2007)
J/AJ/129/1465 : Spectroscopy of red giants in the LMC bar (Cole+, 2005)
J/AJ/120/1808 : Stroemgren photometry in LMC disk (Cole+, 2000)
J/AJ/116/723 : LMC star clusters ages and metallicity (Bica+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Hour of Right Ascension (J2000)
4- 5 I2 min RAm Minute of Right Ascension (J2000)
7- 11 F5.2 s RAs Second of Right Ascension (J2000)
13 A1 --- DE- Sign of the Declination (J2000)
14- 15 I2 deg DEd Degree of Declination (J2000)
17- 18 I2 arcmin DEm Arcminute of Declination (J2000)
20- 23 F4.1 arcsec DEs Arcsecond of Declination (J2000)
25- 29 F5.2 0.1nm W.CaT The CaT index (1)
31- 35 F5.3 0.1nm e_W.CaT The 1σ error in W.CaT
37- 41 F5.2 mag Vmag The V band magnitude
43- 47 F5.2 mag Imag The I band magnitude
49- 53 F5.1 km/s RV Radial velocity
55- 58 F4.1 km/s e_RV The 1σ error in RV
60- 77 A18 --- Comm Additional comment ("No member", "AGB" or
"low S/N") (2)
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Note (1): Defined as ΣCa, the sum of the equivalent widths of the
three CaT lines (848.4-868.2nm)
Note (2): Stars with radial velocity in the range 170≤RVel≤380km/s are
considered LMC members.
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Nomenclature Note:
Stars designated by <[CGH2008] JHHMMSS.ss+DDMMSS.s> in Simbad.
History:
From electronic version of the journal
References:
Gallart et al. Paper I. 2004ApJ...614L.109G 2004ApJ...614L.109G.
Carrera et al. Paper II. 2007AJ....134.1298C 2007AJ....134.1298C. Cat. J/AJ/134/1298.
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jun-2010