J/A+A/579/A104 Abundances in NGC 5053 and NGC 5634 (Sbordone+, 2015)
Chemical abundances of giant stars in NGC 5053 and NGC 5634, two globular
clusters associated with the Sagittarius dwarf Spheroidal galaxy?
Sbordone L., Monaco L., Moni Bidin C., Bonifacio P., Villanova S.,
Bellazzini M., Ibata R., Chiba M., Geisler D., Caffau E., Duffau S.
<Astron. Astrophys. 579, A104 (2015)>
=2015A&A...579A.104S 2015A&A...579A.104S
ADC_Keywords: Clusters, globular ; Stars, giant ; Equivalent widths;
Line Profiles; Abundances, [Fe/H]
Keywords: Galaxy: abundances - globular clusters: individual: NGC 5053 -
globular clusters: individual: NGC 5634 - galaxies: active -
galaxies: abundances - galaxies: individual: Sgr dSph
Abstract:
The tidal disruption of the Sagittarius dwarf Spheroidal galaxy
(Sgr dSph) is producing the most prominent substructure in the Milky
Way (MW) halo, the Sagittarius Stream. Aside from field stars, the Sgr
dSph is suspected to have lost a number of globular clusters (GC).
Many Galactic GC are suspected to have originated in the Sgr dSph.
While for some candidates an origin in the Sgr dSph has been confirmed
due to chemical similarities, others exist whose chemical composition
has never been investigated. NGC 5053 and NGC 5634 are two among these
scarcely studied Sgr dSph candidate-member clusters. To characterize
their composition we analyzed one giant star in NGC 5053, and two in
NGC 5634.
We analize high-resolution and signal-to-noise spectra by means of the
MyGIsFOS code, determining atmospheric parameters and abundances for
up to 21 species between O and Eu. The abundances are compared with
those of MW halo field stars, of "unassociated" MW halo globulars,
and of the metal poor Sgr dSph main body population.
We derive a metallicity of [FeII/H]=-2.26±0.10 for NGC 5053, and of
[FeI/H]=-1.99±0.075 and -1.97±0.076 for the two stars in NGC 5634.
This makes NGC 5053 one of the most metal poor globular clusters in
the MW. Both clusters display an alpha enhancement similar to the one
of the halo at comparable metallicity. The two stars in NGC 5634
clearly display the Na-O anticorrelation widespread among MW
globulars. Most other abundances are in good agreement with standard
MW halo trends.
The chemistry of the Sgr dSph main body populations is similar to the
one of the halo at low metallicity. It is thus difficult to
discriminate between an origin of NGC 5053 and NGC 5634 in the Sgr
dSph, and one in the MW. However, the abundances of these clusters do
appear closer to that of Sgr dSph than of the halo, favoring an origin
in the Sgr dSph system.
Description:
These two tables contain the results relative to the fitting of all
the individual spectral features employed in the analysis. The
"alllines.dat" table contains the feature characteristics (e.g. ion
abundance fitted through the feature, starting and ending
wavelength...), the fitting results (e.g. the derived abundance) and a
star and feature identifiers. The second table (allsynth.txt) contain
the detailed observed and fitted profiles for each feature. Each line
contains the star and feature identifiers, the wavelength of that
specific "pixel" and the corresponding observed and fitted normalized
fluxes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 81 3 *Coordinates, photometry, heliocentric radial
velocities, and determined atmospheric
parameters for the three targets
alllines.dat 104 353 Per-feature fit results
allsynth.dat 49 7411 Feature observed and best-fitting profiles
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Note on table1.dat: Photometric parameters are used for NGC5053-69,
spectroscopic ones for the two stars in NGC 5634 (see Sect. 3.3).
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [NGC]
4- 7 I4 --- NGC Cluster NGC number
9- 16 A8 --- Star Star name
18- 19 I2 h RAh Right ascension (J2000)
21- 22 I2 min RAm Right ascension (J2000)
24- 28 F5.2 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 40 F4.1 arcsec DEs Declination (J2000)
42- 47 F6.3 mag Vmag [14.5/14.8] V magnitude
49- 53 F5.3 mag V-I V-I colour index
55- 59 F5.1 km/s HRV [-21/43] Heliocentric radial velocity
61- 64 I4 K Teff [4085/4450] Effective temperature
66- 69 F4.2 [cm/s2] logg [0.2/1.2] Surface gravity
71- 74 F4.2 km/s Vturb Microturbulent velocity
76- 80 F5.2 [Sun] [Fe/H] [-2.3/-1.9] Metallicity
81 A1 --- n_[Fe/H] [a] a: using [FeII/H] for this star
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Byte-by-byte Description of file: alllines.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Star Star name
10- 11 A2 --- El Element name
13- 14 I2 --- Z [8/63] Atomic number
16- 17 I02 --- Ion [0/1] Ionization state (1)
19- 26 F8.4 nm Wini [481/671] Starting wavelength of fitted feature
28- 35 F8.4 nm Wend [481/671] Ending wavelength of fitted feature
39- 44 F6.3 [Sun] [X/H] [-3/-1] Abundance of the element in [X/H] format
48- 53 F6.3 pm EWf [2/19] Equivalent width of the best fitting
synthetic feature
55- 60 F6.3 pm EWo [2/19] Equivalent width of the observed feature
64- 68 F5.1 --- S/N [46-94] Signal-to-noise ratio at feature center
72- 77 F6.2 km/s Shift [-4/2] Doppler shift applied to the feature
79- 84 F6.4 --- Cont [0.99/1.01] Feature continuum renormalization
88 I1 --- VTuse [0/1] Flag for use in Vt determination (2)
90 I1 --- Tuse [0/1] Flag for use in Teff determination (3)
94-104 A11 --- Feat Feature ID (4)
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Note (1): 00 = neutral, 01 = one time ionized etc.
Note (2): If VTuse = 1, the feature has been used in determining the slope of
the EW-Abundance relation used to set Microturbulence (meaningful only for
FeI features).
Note (3): If Tuse = 1, the feature has used to determined the LEAS used in
estimating effective temperature (meaningful only for Fe I features).
Note (4): Composed of Z, Ion and central wavelength multiplied by 1000 and
truncated.
For Z=30, Ion=00 and lambda=481.0280-481.0660Å, Feat = 3000_481047.
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Byte-by-byte Description of file: allsynth.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Star Star name
10- 20 A11 --- Feat Feature ID
24- 33 F10.6 nm lambda [481/671] Wavelength λ
36- 41 F6.4 --- Fsynth [0.2/1.1] Best-fitting synthetic normalized
flux (1)
44- 49 F6.4 --- Fobs [0.2/1.1] Observed normalized flux
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Note (1): To overplot the best fitting synthetic over the observed spectrum,
synth must be DIVIDED by the 'Cont' continuum renormalization given in
the alllines.dat table for the feature.
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Acknowledgements:
Luca Sbordone, lsbordon(at)astro.puc.cl
(End) Luca Sbordone [MAS - PUC, Chile], Patricia Vannier [CDS] 19-May-2015