J/A+A/580/A121 CaT/[Fe/H] calibration for Galactic bulge stars (Vasquez+, 2015)
Calcium triplet metallicity calibration for stars in the Galactic bulge.
Vasquez S., Zoccali M., Hill V., Gonzalez O.A., Saviane I., Rejkuba M.,
Battaglia G.
<Astron. Astrophys. 580, A121 (2015)>
=2015A&A...580A.121V 2015A&A...580A.121V
ADC_Keywords: Milky Way ; Stars, K-type ; Spectroscopy ; Abundances, [Fe/H]
Keywords: stars: abundances - Galaxy: bulge - techniques: spectroscopic
Abstract:
We present a new calibration of the calcium II triplet equivalent
widths versus [Fe/H], constructed upon K giant stars in the Galactic
bulge. This calibration will be used to derive iron abundances for the
targets of the GIBS survey, and is in general especially well suited
for solar and supersolar metallicity giants, which are typical of
external massive galaxies. To obtain the calibration, about 150 bulge
K giants were observed with the GIRAFFE spectrograph at the VLT with a
resolution of R∼20000 and at R∼6000. In the first case, the spectra
allowed us to directly determine the Fe abundances from several
unblended Fe lines, deriving what we call here high-resolution [Fe/H]
measurements. The low-resolution spectra allowed us to measure
equivalent widths of the two strongest lines of the near-infrared
calcium II triplet at 8542 and 8662Å. By comparing the two
measurements, we derived a relation between calcium equivalent widths
and [Fe/H] that is linear over the metallicity range probed here,
-1<[Fe/H]<+0.7. By adding a small second-order correction based on
literature globular cluster data, we derived the unique calibration
equation [Fe/H]CaT=-3.150+0.432W'+0.006W'2, with an rms dispersion
of 0.197dex, valid across the whole metallicity range
-2.3<[Fe/H]<+0.7.
Description:
The target stars we used to construct the CaT calibration are all
located in Baade's Window, and they consist of two samples: 80 stars
in the bulge RC and 68 stars on the RGB, which are ∼0.7mag brigther
than the RC. The medium-resolution spectra analysed here were taken
with the FLAMES-GIRAFFE multifibre spectrograph at the VLT, in Medusa
mode, within the ESO program ID 385.B-0735(B).
Bulge data used to compute the metallicity calibration are presented.
For each bulge star we provided the coordinates, magnitude difference
respect to the red clump, equivalent widths for the two strongest
calcium lines and the corresponding metallicity derived from high
resolution spectroscopy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 76 148 Calcium triplet metallicity calibration for
bulge stars
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Field [RGB RC] Bulge field: Red Giant Branch or
Red Clump
5- 10 I6 --- ID [44560/596502] Identification number
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 22 F5.2 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 34 F4.1 arcsec DEs Declination (J2000)
36- 41 F6.3 mag dKmag [-1.77/0.28] K-KRC magnitude difference
43- 47 F5.3 0.1nm EW2 Equivalent width at 8542.09Å
49- 53 F5.3 0.1nm e_EW2 Uncertainty for EW2
55- 59 F5.3 0.1nm EW3 Equivalent width at 8662.14Å
61- 65 F5.3 0.1nm e_EW3 Uncertainty for EW3
67- 71 F5.2 [Sun] [Fe/H] [-1.44/0.62] High resolution metallicity
73- 76 F4.2 [Sun] e_[Fe/H] [0.08/0.49] Uncertainty for [Fe/H]
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Acknowledgements:
Sergio Vasquez, svasquez(at)astro.puc.cl
(End) Patricia Vannier [CDS] 17-Jul-2015