J/A+A/533/A69 Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)
Multiple stellar populations in the globular cluster NGC 1851
Carretta E., Lucatello S., Gratton R., Bragaglia A, D'Orazi V.
<Astron. Astrophys. 533, A69 (2011)>
=2011A&A...533A..69C 2011A&A...533A..69C
ADC_Keywords: Clusters, globular ; Stars, giant; Stars, population II ;
Radial velocities ; Effective temperatures ; Abundances
Keywords: stars: abundances - stars: atmospheres - globular clusters: general -
globular clusters: individual: NGC 1851 - stars: Population II
Abstract:
We present a detailed chemical tagging of individual stellar
populations in the Galactic globular cluster (GC) NGC 1851. Abundances
are derived from FLAMES spectra for the largest sample of giants (124)
and the widest number of elements ever analysed in this peculiar GC.
The chemistry is characterised using homogeneous abundances of
proton-capture (O, Na, Mg, Al, Si), α-capture (Ca, Ti), Fe-peak
(Sc, V, Mn, Co, Ni, Cu), and neutron-capture elements (Y, Zr, Ba, La,
Ce, Nd, Eu, Dy). We confirm the presence of an [Fe/H] spread larger
than the observational errors in this cluster, but too small to
clearly separate different sub-populations. We instead propose a
classification scheme using a combination of Fe and Ba (which is much
more abundant in the more metal-rich group) by means of a cluster
analysis. With this approach, we separated stars into two components
of a metal-rich (MR) and a metal-poor (MP) population. Each component
displays a Na-O anticorrelation, which is a signature of a genuine GC,
but has different ratios of primordial (FG) to polluted (SG) stars.
Moreover, clear (anti)correlations of Mg and Si with Na and O are
found for each component. The level of [α/H] tracks iron and is
higher in the MR population, which might therefore have received an
additional contribution from core-collapse supernovae. When
considering all s-process elements, the MR population shows a larger
enrichment than the MP one. This is probably due to the contribution
of intermediate-low mass stars, because we find that the level of
heavy s-process elements is higher than that of light s-process nuclei
in the MR stars; however, a large contribution from low mass stars is
unlikely, because it would likely cancel the O-Na anticorrelation.
Finally, we confirm the presence of correlations between the amount of
proton-capture elements and the level of s-process elements previously
found by other investigations, at least for the MR population. This
finding apparently requires a quite long delay for the second
generation of the MR component. Scenarios for the formation of NGC
1851 appear complex, and are not yet well understood. A merger of two
distinct GCs in a parent dwarf galaxy, each cluster with a different
Ba level and an age difference of ∼1Gyr, might explain (i) the double
subgiant branch, (ii) a possible difference in C content between the
two original GCs, and (iii) the Stromgren photometry of this peculiar
cluster. However, the correlation existing between p-capture and
n-capture elements within the MR population requires the additional
assumption of a long delay for its second generation. More
observations are required to fully understand the formation of this
GC.
Description:
For a sample of 124 RGB stars in NGC 1851 observed with FLAMES we
present abundances of Fe, O, Na, Mg, Al, Si, Ca, Ti, Sc, V, Mn, Co,
Ni, Cu, Y, Zr, Ba, La, Ce, Nd, Eu, Dy. n-capture elements (except Ba)
are available only for the 13 stars observed with UVES-FLAMES.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 124 Identification, positions, B, V, K, RV, flag
table3.dat 58 124 Teff, logg, [A/H], Vt, [Fe/H]I, [Fe/H]II
table4.dat 61 124 [O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe]
table5.dat 55 124 [Si/Fe], [Ca/Fe], [Ti/Fe] I & II
table6.dat 97 124 [Sc/Fe], [V/Fe], [Cr/Fe], [Mn/Fe], [Co/Fe], [Ni/Fe],
[Cu/Fe]
table7.dat 96 13 [Y/Fe], [Zr/Fe], [La/Fe], [Ce/Fe]. [Nd/Fe], [Eu/Fe],
[Dy/Fe]
table8.dat 18 124 [Ba/Fe]
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See Also:
J/PASP/104/1063 : BV Color-Magnitude Diagram for NGC 1851 (Walker 1992)
J/A+A/333/479 : NGC1851 dynamical and evolutionary properties (Saviane+ 1998)
J/A+A/525/A148 : Radial velocities in two globular clusters (Scarpa+, 2011)
J/AJ/122/2569 : VI photometry of NGC 288, 362 and 1851 (Bellazzini+, 2001)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7 I1 h RAh Right ascension (J2000.0)
9- 10 I2 min RAm Right ascension (J2000.0)
12- 17 F6.3 s RAs Right ascension (J2000.0)
19 A1 --- DE- Declination sign (J2000.0)
20- 21 I2 deg DEd Declination (J2000.0)
23- 24 I2 arcmin DEm Declination (J2000.0)
26- 30 F5.2 arcsec DEs Declination (J2000.0)
32- 37 F6.3 mag Bmag B magnitude
39- 44 F6.3 mag Vmag V magnitude
46- 51 F6.3 mag Kmag K magnitude (2MASS)
53- 58 F6.2 km/s RV Heliocentric radial velocity
60- 68 A9 --- Inst Intrument: UVES, Giraffe-HR11, or Giraffe-HR13
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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- 5 I5 --- ID Identification number
7- 10 I4 K Teff Effective temperature
12- 15 F4.2 [cm/s2] logg Gravity
17- 21 F5.2 [Sun] [A/H] Metallicity
23- 26 F4.2 km/s vt Microturbulent velocity ξ
28- 29 I2 --- o_[Fe/H]1 Number of FeI lines
31- 36 F6.3 [Sun] [Fe/H]1 Iron I abundance
38- 42 F5.3 [Sun] e_[Fe/H]1 Error on [Fe/H]1
44- 45 I2 --- o_[Fe/H]2 ? Number of FeII lines
47- 52 F6.3 [Sun] [Fe/H]2 ? Iron II abundance
54- 58 F5.3 [Sun] e_[Fe/H]2 ? Error on [Fe/H]2
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7 I1 --- o_[O/Fe] ? Number of O lines
9- 13 F5.2 [Sun] [O/Fe] ? Oxygen abundance
15- 18 F4.2 [Sun] e_[O/Fe] ? rms uncertainty on [O/Fe]
20 I1 --- o_[Na/Fe] ? Number of Na lines
22- 26 F5.2 [Sun] [Na/Fe] ? Sodium abundance
28- 31 F4.2 [Sun] e_[Na/Fe] ? rms uncertainty on [Na/Fe]
33 I1 --- o_[Mg/Fe] ? Number of Mg lines
35- 39 F5.2 [Sun] [Mg/Fe] ? Magnesium abundance
41- 44 F4.2 [Sun] e_[Mg/Fe] ? rms uncertainty on [Mg/Fe]
46 I1 --- o_[Al/Fe] ? Number of Al lines
48- 52 F5.2 [Sun] [Al/Fe] ? Aluminum abundance
54- 57 F4.2 [Sun] e_[Al/Fe] ? rms uncertainty on [Al/Fe]
59 A1 --- l_[O/Fe] [0,1] 0 = upper limit in [O/Fe]
61 A1 --- l_[Al/Fe] [0,1]? 0 = upper limit in [Al/Fe]
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7- 8 I2 --- o_[Si/Fe] ? Number of Si lines
10- 14 F5.2 [Sun] [Si/Fe] ? Silicon abundance
16- 19 F4.2 [Sun] e_[Si/Fe] ? rms uncertainty on [Si/Fe]
21- 22 I2 --- o_[Ca/Fe] ? Number of Ca lines
24- 28 F5.2 [Sun] [Ca/Fe] ? Calcium abundance
30- 33 F4.2 [Sun] e_[Ca/Fe] ? rms uncertainty on [Ca/Fe]
35- 36 I2 --- o_[Ti/Fe]1 ? Number of Ti I lines
38- 42 F5.2 [Sun] [Ti/Fe]1 ? Titanium I abundance
44- 47 F4.2 [Sun] e_[Ti/Fe]1 ? rms uncertainty on [Si/Fe]
49 I1 --- o_[Ti/Fe]2 ? Number of Ti II lines
51- 55 F5.2 [Sun] [Ti/Fe]2 ? Titanium II abundance
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7 I1 --- o_[Sc/Fe] Number of Sc lines
9- 13 F5.2 [Sun] [Sc/Fe] Scandium abundance
15- 18 F4.2 [Sun] e_[Sc/Fe] ? rms uncertainty on [Sc/Fe]
20 I1 --- o_[V/Fe] ? Number of V lines
22- 26 F5.2 [Sun] [V/Fe] ? Vanadium abundance
28- 31 F4.2 [Sun] e_[V/Fe] ? rms uncertainty on [V/Fe]
33 I1 --- o_[Cr/Fe] ? Number of Cr lines
35- 39 F5.2 [Sun] [Cr/Fe] ? Cromium abundance
41- 44 F4.2 [Sun] e_[Cr/Fe] ? rms uncertainty on [Cr/Fe]
46 I1 --- o_[Mn/Fe] ? Number of Mn lines
48- 52 F5.2 [Sun] [Mn/Fe] ? Manganese abundance
54- 57 F4.2 [Sun] e_[Mn/Fe] ? rms uncertainty on [Mn/Fe]
59 I1 --- o_[Co/Fe] ? Number of Co lines
61- 65 F5.2 [Sun] [Co/Fe] ? Cobalt abundance
67- 70 F4.2 [Sun] e_[Co/Fe] ? rms uncertainty on [Co/Fe]
72- 73 I2 --- o_[Ni/Fe] ? Number of Ni lines
75- 79 F5.2 [Sun] [Ni/Fe] ? Nichel abundance
81- 84 F4.2 [Sun] e_[Ni/Fe] ? rms uncertainty on [Ni/Fe]
86 I1 --- o_[Cu/Fe] ? Number of Cu lines
88- 92 F5.2 [Sun] [Cu/Fe] ? Copper abundance
94- 97 F4.2 [Sun] e_[Cu/Fe] ? rms uncertainty on [Cu/Fe]
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7 I1 --- o_[Y/Fe] ? Number of Y II lines
9- 13 F5.2 [Sun] [Y/Fe] ? Yttrium abundance
15- 18 F4.2 [Sun] e_[Y/Fe] ? rms uncertainty on [Y/Fe]
20 I1 --- o_[Zr/Fe] ? Number of Zr II lines
22- 26 F5.2 [Sun] [Zr/Fe] ? Zirconium abundance
28- 31 F4.2 [Sun] e_[Zr/Fe] ? rms uncertainty on [Zr/Fe]
33 I1 --- o_[La/Fe] ? Number of La II lines
35- 39 F5.2 [Sun] [La/Fe] ? Lanthanum abundance
41- 44 F4.2 [Sun] e_[La/Fe] ? rms uncertainty on [La/Fe]
46 I1 --- o_[Ce/Fe] ? Number of Ce II lines
48- 52 F5.2 [Sun] [Ce/Fe] ? Cerium abundance
54- 57 F4.2 [Sun] e_[Ce/Fe] ? rms uncertainty on [Ce/Fe]
59 I1 --- o_[Nd/Fe] ? Number of Nd II lines
61- 65 F5.2 [Sun] [Nd/Fe] ? Neodimium abundance
67- 70 F4.2 [Sun] e_[Nd/Fe] ? rms uncertainty on [Nd/Fe]
72 I1 --- o_[Eu/Fe] ? Number of Eu II lines
74- 78 F5.2 [Sun] [Eu/Fe] ? Europium abundance
80- 83 F4.2 [Sun] e_[Eu/Fe] ? rms uncertainty on [Eu/Fe]
85 I1 --- o_[Dy/Fe] ? Number of Dy II lines
87- 91 F5.2 [Sun] [Dy/Fe] ? Dysprosium abundance
93- 96 F4.2 [Sun] e_[Dy/Fe] ? rms uncertainty on [Dy/Fe]
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Identification number
7 I1 --- o_[Ba/Fe] ? Number of Ba II lines
9- 13 F5.2 [Sun] [Ba/Fe] ? Barium abundance
15- 18 F4.2 [Sun] e_[Ba/Fe] ? rms uncertainty on [Ba/Fe]
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Acknowledgements:
Eugenio Carretta, eugenio.carretta(at)oabo.inaf.it
(End) Francois Ochsenbein [CDS] 28-Jul-2011