J/A+A/590/A9 RGB stars in Galactic GC stellar parameters (Dias+, 2016)
FORS2/VLT survey of Milky Way globular clusters.
II. Fe and Mg abundances of 51 Milky Way globular clusters on a homogeneous
scale.
Dias B., Barbuy B., Saviane I, Held E., Da Costa G., Ortolani S.,
Gullieuszik M., Vasquez S.
<Astron. Astrophys. 590, A9 (2016)>
=2016A&A...590A...9D 2016A&A...590A...9D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Stars, giant ; Abundances ;
Radial velocities ; Spectroscopy ; Effective temperatures ;
Models, atmosphere
Keywords: stars: abundances - stars: kinematics and dynamics -
stars: Population II - Galaxy: stellar content - Galaxy: evolution -
globular clusters: general
Abstract:
Globular clusters trace the formation and evolution of the Milky Way
and surrounding galaxies, and outline their chemical enrichment
history. To accomplish these tasks it is important to have large
samples of clusters with homogeneous data and analysis to derive
kinematics, chemical abundances, ages and locations.
We aim to obtain homogeneous metallicities and alpha-element
enhancement for 51 Galactic bulge, disc, and halo globular clusters
that are among the most distant and/or highly reddened in the
Galaxy's globular cluster system. We also provide membership
selection based on stellar radial velocities and atmospheric
parameters. The implications of our results are discussed.
We observed R∼2000 spectra in the wavelength interval 456-586nm for
over 800 red giant stars in 51 Galactic globular clusters. We applied
full spectrum fitting with the code ETOILE together with libraries of
observed and synthetic spectra. We compared the mean abundances of all
clusters with previous work and with field stars. We used the relation
between mean metallicity and horizontal branch morphology defined by
all clusters to select outliers for discussion.
[Fe/H], [Mg/Fe], and [alpha/Fe] were derived in a consistent way for
almost one-third of all Galactic globular clusters. We find our
metallicities are comparable to those derived from high-resolution
data to within sigma=0.08dex over the interval -2.5<[Fe/H]<0.0.
Further, a comparison of previous metallicity scales with ours yields
sigma<0.16dex. We also find that the distribution of [Mg/Fe] and
[alpha/Fe] with [Fe/H] for the 51 clusters follows the general trend
exhibited by field stars. It is the first time that the following
clusters are included in a large sample of homogeneous stellar
spectroscopic observations and metallicity derivation: BH 176,
Djorg 2, Pal 10, NGC 6426, Lynga 7, and Terzan 8. In particular, the
first three clusters only had photometric metallicities previously and
the available metallicity for NGC 6426 was based only on integrated
spectroscopy and photometry. Two other clusters, HP 1 and NGC 6558,
are confirmed as candidates for the oldest globular clusters in the
Milky Way.
Stellar spectroscopy in the visible at R∼2000 for a large sample of
globular clusters is a robust and efficient way to trace the chemical
evolution of the host galaxy and to detect interesting objects for
follow-up at higher-resolution and with forthcoming giant telescopes.
The technique used here can also be applied to globular cluster
systems in nearby galaxies with current instruments and to distant
galaxies with the advent of ELTs.
Description:
Spectroscopic parameters for 758 red giant branch stars in 51 Milky
Way globular clusters. For each star star ID, cluster name, equatorial
coordinates, magnitude, colour, heliocentric velocities, membership
classification member, effective temperature, surface gravity,
metallicity, Mg and alpha-element abundance. We note that magnitude
and colours are not calibrated.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 115 758 Identification of cluster stars including
photometric and kinematics information
tablea2.dat 126 758 Atmospheric parameters for RGB stars
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See also:
J/A+A/540/A27 : Spectroscopy in Galactic globular clusters (Saviane+, 2012)
J/A+A/573/A13 : Metal abundances in 6 globular cluster (Dias+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Star Star identification (G1)
15- 21 A7 --- Cl.ID Cluster identification
23- 33 A11 --- Cl.Name Cluster name
35- 44 F10.6 deg RAdeg Right ascension (J2000)
46- 55 F10.6 deg DEdeg Declination (J2000)
57- 58 I2 h RAh Right ascension (J2000.0)
60- 61 I2 min RAm Right ascension (J2000.0)
63- 66 F4.1 s RAs Right ascension (J2000.0)
68 A1 --- DE- Declination sign (J2000.0)
69- 70 I2 deg DEd Declination (J2000.0)
72- 73 I2 arcmin DEm Declination (J2000.0)
75- 78 F4.1 arcsec DEs Declination (J2000.0)
80- 84 F5.2 mag Vmag V magnitude (2)
86- 91 F6.3 mag V-I ? V-I colour index (2)
93- 98 F6.3 mag B-V ? B-V colour index (2)
100-103 I4 km/s HV Heliocentric velocity
105-113 F9.4 km/s HVt ? Heliocentric velocity from CaT (3)
115 A1 --- Mmb [M] Membership (M=member)
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Note (2): magnitudes and colours are not calibrated, they were used to select
the targets from the red giant branch in the pre-images.
Note (3): The velocities from CaT were taken from from Saviane et al.
(2012A&A...540A..27S 2012A&A...540A..27S, Cat. J/A+A/540/A27) and from Vasquez et al. (in prep.)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Star Star identification (G1)
15- 18 I4 K TeffM Effective temperature from MILES library
20- 22 I3 K e_TeffM rms uncertainty on TeffM
24- 27 I4 K TeffC Effective temperature from Coelho library
29- 31 I3 K e_TeffC rms uncertainty on TeffM
33- 36 I4 K Teff Average of MILES and Coelho effective
temperature (adopted)
38- 40 I3 K e_Teff rms uncertainty on Teff
42- 45 F4.2 [cm/s2] loggM Surface gravity from MILES library
47- 50 F4.2 [cm/s2] e_loggM rms uncertainty on loggM
52- 55 F4.2 [cm/s2] loggC Surface gravity from Coelho library
57- 60 F4.2 [cm/s2] e_loggC rms uncertainty on loggC
62- 65 F4.2 [cm/s2] logg Average of MILES and Coelho surface gravity
67- 70 F4.2 [cm/s2] e_logg rms uncertainty on loggC
72- 76 F5.2 [Sun] [Fe/H]M Metallicity from MILES library
78- 81 F4.2 [Sun] e_[Fe/H]M rms uncertainty on [Fe/H]M
83- 87 F5.2 [Sun] [Fe/H]C Metallicity from Coelho library
89- 92 F4.2 [Sun] e_[Fe/H]C rms uncertainty on [Fe/H]C
94- 98 F5.2 [Sun] [Fe/H] Average of MILES and Coelho metallicity
100-103 F4.2 [Sun] e_[Fe/H] rms uncertainty on [Fe/H]
105-109 F5.2 [Sun] [Mg/Fe] Abundance [Mg/Fe] rom MILES library
111-114 F4.2 [Sun] e_[Mg/Fe] rms uncertainty on [Mg/Fe]
116-119 F4.2 [Sun] [a/Fe] Abundance [alpha/Fe] from Coelho library
121-124 F4.2 [Sun] e_[a/Fe] rms uncertainty on [alpha/Fe]
126 A1 --- Mmb [M] Membership (M=member)
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Global notes:
Note (G1): Stars identified as Cl.Name_NNN (as example 47Tuc_502).
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Acknowledgements:
Ivo Saviane, isaviane(at)eso.org and
Sergio Vasquez, svasquez(at)astro.puc.cl
References:
Saviane et al., 2012A&A...540A..27S 2012A&A...540A..27S, Cat. J/A+A/540/A27
Homogeneous metallicities and radial velocities for Galactic globular
clusters. First CaT metallicities for twenty clusters
Vasquez et al., 2016, in prep.
Homogeneous Metallicities and Radial Velocities for Galactic Globular
Clusters. II New CaT metallicities for 28 faint and redden globular clusters
Dias et al., 2015A&A...573A..13D 2015A&A...573A..13D, Cat. J/A+A/573/A13
FORS2/VLT survey of Milky Way globular clusters. I. Description of the
method for derivation of metal abundances in the optical and application to
NGC 6528, NGC 6553, M 71, NGC 6558, NGC 6426, and Terzan 8.
(End) Bruno Dias [ESO, Chile], Patricia Vannier [CDS] 10-Mar-2016