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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 77 635 LMC RGB stars observed
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
Bytes Format Units Label Explanations
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)
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.
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. Carrera et al. Paper II. 2007AJ....134.1298C. Cat. J/AJ/134/1298.
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Jun-2010
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