J/A+A/563/A76 CaII triplet equivalent widths in 30 globulars (Mauro+, 2014)
Deriving metallicities from calcium triplet spectroscopy in combination with
near-infrared photometry.
Mauro F., Moni Bidin C., Geisler D., Saviane I., Da Costa G.S.,
Gormaz-Matamala A.C., Vasquez S., Chene A.-N., Cohen R., Dias B.
<Astron. Astrophys. 563, A76 (2014)>
=2014A&A...563A..76M 2014A&A...563A..76M
ADC_Keywords: Clusters, globular ; Stars, giant ; Photometry, infrared ;
Equivalent widths
Keywords: stars: abundances - globular clusters: general -
stars: kinematics and dynamics
Abstract:
When they are established with sufficient precision, the ages,
metallicities and kinematics of Galactic globular clusters (GGCs) can
shed much light on the dynamical and chemical evolution of the
Galactic halo and bulge. While the most fundamental way of determining
GC abundances is by mean high-resolution spectroscopy, in practice
this method is limited to only the brighter stars in the nearest and
less reddened objects. This restriction has, over the years, led to
the development of a large number of techniques that measure the
overall abundance indirectly from parameters that correlate with
overall metallicity. One of the most efficient methods is measuring of
the equivalent width (EW) of the calcium II triplet (CaT) at
λ≈8500Å in red giants, which are corrected for the
luminosity and temperature effects using the V magnitude differences
from the horizontal branch (HB).
We establish a similar method in the near-infrared (NIR), by combining
the power of the differential magnitudes technique with the advantages
of NIR photometry to minimize differential reddening effects.
We used the Ks magnitude difference between the star and the reddest
part of the HB (RHB) or of the red clump (RC) to generate reduced
equivalent widths (rEW) from the previously presented datasets. Then
we calibrated these rEW against three previously reported different
metallicity scales; one of which we corrected using high-resolution
spectroscopic metallicities.
Description:
Our main target list consists of the GCs analyzed by S12 (Saviane et
al., 2012, Cat. J/A+A/540/A27). The NIR imaging collected in the
context of the VVV Survey was used for all clusters included in the
survey area. We also checked whether any of the GCs in the dataset not
observed by the VVV Survey had useful 2MASS photometry, that would
permit us to determine the RHB position.
We similarly selected GCs from the R97 (Rutledge et al.,
1997PASP..109..907R 1997PASP..109..907R) catalog to determine a calibration for this
dataset as well
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 24 30 List of reddest parts of the Horizontal Branch
(RHB) levels in the 30 glubular clusters
table8.dat 93 443 Equivalent widths of the Ca-II triplet
(λ∼850nm)
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See also:
J/A+A/540/A27 : Spectroscopy in Galactic globular clusters (Saviane+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name
9- 13 A5 --- Phot Reference for photometry in table8 (1)
15- 19 F5.2 mag Ksmag(HB) Ks magnitude HB-level
21- 24 F4.2 mag e_Ksmag(HB) rms uncertainty on Ksmag(HB)
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Note (1): Reference as follows:
VVV = VVV survey, Minniti et al., 2010NewA...15..433M 2010NewA...15..433M
2MASS = 2MASS, Cutri et al., Cat. II/246
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Cluster Cluster name
9- 19 F11.7 deg RAdeg Star right ascension (J2000)
21- 31 F11.7 deg DEdeg Star declination (J2000)
33- 39 F7.4 mag Jmag J magnitude (1)
41- 46 F6.4 mag e_Jmag rms uncertainty on Jmag
48- 54 F7.4 mag Hmag H magnitude (1)
56- 61 F6.4 mag e_Hmag rms uncertainty on Hmag
63- 69 F7.4 mag Ksmag Ks magnitude (1)
71- 76 F6.4 mag e_Ksmag rms uncertainty on Ksmag
78- 82 F5.3 0.1nm EW CaT equivalent width (Å)
84- 88 F5.3 0.1nm e_EW rms uncertainty on EW
91- 93 A3 --- Ref Reference (2)
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Note (1): From VVV or 2MASS, as indicated in table1.dat.
Note (2): Reference as follows:
S12 = Saviane et al., 2012, Cat. J/A+A/540/A27
R97 = Rutledge et al., 1997PASP..109..907R 1997PASP..109..907R
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Acknowledgements:
Francesco Mauro, skz5k2(at)gmail.com
(End) Patricia Vannier [CDS] 04-Mar-2014