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J/AJ/136/1039     CaII index of SMC red giant branch stars      (Carrera+, 2008)

The chemical enrichment history of the Small Magellanic Cloud and its gradients. Carrera R., Gallart C., Aparicio A., Costa E., Mendez R.A., Noel N.E.D. <Astron. J., 136, 1039-1048 (2008)> =2008AJ....136.1039C
ADC_Keywords: Magellanic Clouds ; Stars, giant ; Spectra, infrared ; Radial velocities ; Photometry, VRI Keywords: galaxies: evolution - galaxies: individual (SMC) - galaxies: stellar content - Local Group - Magellanic Clouds Abstract: We present stellar metallicities derived from Ca II triplet spectroscopy in over 350 red giant branch stars in 13 fields distributed in different positions in the Small Magellanic Cloud, ranging from ∼1° to ∼4° from its center. In the innermost fields, the average metallicity is [Fe/H]~-1. This value decreases when we move away toward outermost regions. This is the first detection of a spectroscopic metallicity gradient in this galaxy. We show that the metallicity gradient is related to an age gradient, in the sense that more metal-rich stars, which are also younger, are concentrated in the central regions of the galaxy. Description: The spectroscopic observations were carried on in service mode with the VLT Antu telescope, at Paranal Observatory (Chile), through program 074.B-0446. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 67 372 Red giants stars observed
See also: J/AJ/131/2514 : Radial velocities of red giants in the SMC (Harris+, 2006) J/AJ/135/836 : Calcium triplet index in LMC stars (Carrera+, 2008) Byte-by-byte Description of file: table2.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- 10 F4.1 s RAs Second of Right Ascension (J2000) 12 A1 --- DE- Sign of the Declination (J2000) 13- 14 I2 deg DEd Degree of Declination (J2000) 16- 17 I2 arcmin DEm Arcminute of Declination (J2000) 19- 22 F4.1 arcsec DEs Arcsecond of Declination (J2000) 24- 28 F5.2 0.1nm W.CaT The CaT index (1) 30- 33 F4.2 0.1nm e_W.CaT The 1σ uncertainty in W.CaT 35- 39 F5.2 mag Vmag ?=99.99 The V band magnitude 41- 45 F5.2 mag Imag ?=99.99 The I band magnitude 47- 52 F6.1 km/s RV Radial velocity 54- 57 F4.1 km/s e_RV The 1σ uncertainty in RV 59- 67 A9 --- Comm Additional comment ("AGB", "AGB?" or "No member")
Note (1): Defined as ΣCa, the sum of the equivalent widths of the three CaT lines (848.4-868.2nm). The metallicity is given by: [Fe/H] =-2.95+0.3ΣCa+0.23MI, where MI is the absolute I magnitude, and [Fe/H] is in the Carretta & Gratton scale (1997, Cat. J/A+AS/121/95) metallicity scale.
Nomenclature Note: Sources identified as <[CGA2008] JHHMMSS.s+DDMMSS.s> in Simbad History: From electronic version of the journal References: Noel et al., Paper I 2007AJ....133.2037N Carrera et al., Paper II 2007AJ....134.1298C, Cat. J/AJ/134/1298 Carrera et al., Paper III 2008AJ....135..836C, Cat. J/AJ/135/836
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 06-Apr-2011
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