J/MNRAS/455/199 CaII triplet in red giant spectra (Da Costa, 2016)
The CaII triplet in red giant spectra: [Fe/H] determinations and the role
of [Ca/Fe].
Da Costa G.S.
<Mon. Not. R. Astron. Soc., 455, 199-206 (2016)>
=2016MNRAS.455..199D 2016MNRAS.455..199D (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Equivalent widths ;
Radial velocities
Keywords: techniques: spectroscopic - stars: abundances - stars: Population II -
globular clusters: general - Magellanic Clouds
Abstract:
Measurements are presented and analysed of the strength of the CaII
triplet lines in red giants in Galactic globular and open clusters,
and in a sample of red giants in the LMC disc that have significantly
different [Ca/Fe] abundance ratios to the Galactic objects. The
Galactic objects are used to generate a calibration between CaII
triplet line strength and [Fe/H], which is then used to estimate
[Fe/H]CaT for the LMC stars. The values are then compared with the
[Fe/H]spec determinations from high-dispersion spectroscopy. After
allowance for a small systematic offset, the two abundance
determinations are in excellent agreement. Further, as found in
earlier studies, the difference is only a very weak function of the
[Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to -0.2 causes
the CaII-based abundance to underestimate [Fe/H]spec by only ∼0.15dex,
assuming a Galactic calibration. Consequently, the CaII triplet
approach to metallicity determinations can be used without significant
bias to study stellar systems that have substantially different
chemical evolution histories.
Description:
The data for this study consist of observations of Galactic globular
and open clusters, which are used to provide a calibration between
CaII triplet line strength and abundance [Fe/H], and observations
of a sample of red giants in the disc of the LMC originally studied at
high dispersion by Pompeia et al. (2008, Cat. J/A+A/480/379), and for
which an updated analysis is available in Van der Swaelmen et al.
(2013, Cat. J/A+A/560/A44). All observations were carried out at the
Anglo-Australian Telescope using the 2dF multi-object fibre positioner
and the AAOmega dual beam spectrograph1. The red arm of the
spectrograph was configured with the 1700D grating centred at
∼8600Å to give coverage of the CaII triplet lines with a resolution
R of approximately 10000. The corresponding blue spectra are not used
in this work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
clusters.dat 43 7 List of studied clusters
table3.dat 58 162 Observational data for cluster member stars
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See also:
J/A+A/480/379 : Abundances of 59 red giants in LMC (Pompeia+, 2008)
J/A+A/560/A44 : Abundances of LMC bar and disk stars (Van der Swaelmen+, 2013)
Byte-by-byte Description of file: clusters.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Cluster Cluster name
15- 16 I2 h RAh Simbad right ascension (J2000)
18- 19 I2 min RAm Simbad right ascension (J2000)
21- 25 F5.2 s RAs Simbad right ascension (J2000)
27 A1 --- DE- Simbad declination sign (J2000)
28- 29 I2 deg DEd Simbad declination (J2000)
31- 32 I2 arcmin DEm Simbad declination (J2000)
34- 37 F4.1 arcsec DEs ? Simbad declination (J2000)
39- 43 A5 --- Cl Cluster abbreviation for stars in table3
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- ID Star name
13- 14 I2 h RAh Right ascension (J2000)
16- 17 I2 min RAm Right ascension (J2000)
19- 23 F5.2 s RAs Right ascension (J2000)
25 A1 --- DE- Declination sign (J2000)
26- 27 I2 deg DEd Declination (J2000)
29- 30 I2 arcmin DEm Declination (J2000)
32- 35 F4.1 arcsec DEs Declination (J2000)
37- 41 F5.2 mag Vmag V magnitude
43- 46 F4.2 0.1nm W(8542) Reduced equivalent width of CaII 8542Å
line (1)
48- 51 F4.2 0.1nm W(8662) Reduced equivalent width of CaII 8662Å
line (1)
53- 58 F6.1 km/s RV Radial velocity
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Note (1): reduced equivalent width W', which is defined as the value of
ΣW at V-VHB=0.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Jul-2016