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J/A+A/614/A146      Stellar parameters of NGC3201 RGB stars       (Dias+, 2018)

Galactic or extragalactic chemical tagging for NGC3201? Discovery of an anomalous CN-CH relation. Dias B., Araya, I., Nogueira-Cavalcante J.P., Saker L., Shokry A. <Astron. Astrophys. 614, A146 (2018)> =2018A&A...614A.146D (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Stars, giant ; Abundances, peculiar ; Spectroscopy Keywords: (Galaxy:) globular clusters: individual: NGC 3201 - stars: abundances - Galaxy: halo - stars: Population II Abstract: The origin of the globular cluster (GC) NGC3201 is under debate. Its retrograde orbit points to an extragalactic origin, but no further chemical evidence supports this idea. Light-element chemical abundances are useful to tag GCs and can be used to shed light in this discussion. Recently it was shown that the CN and CH indices are useful to identify anomalous GCs out of typical Milky Way GCs. A possible origin of anomalous clusters is the merger of two GCs and/or nucleus of a dwarf galaxy. We aim at deriving CN and CH band strengths for red giant stars in NGC3201 and compare with photometric indices and high-resolution spectroscopy and discuss in the context of GC chemical tagging. We measure molecular band indices of S(3839) and G4300 for CN and CH, respectively from low-resolution spectra of red giant stars. Gravity and temperature effects are removed. Photometric indices are used to indicate further chemical information on C+N+O or s-process element abundances, not derived from low-resolution spectra. We found three groups on the CN-CH distribution. A main sequence (S1), a secondary less-populated sequence (S2), and a group of peculiar (pec) CN-weak and CH-weak stars, one of which was previously known. The three groups seem to have different C+N+O and/or s-process element abundances, to be confirmed by high-resolution spectroscopy. These are typical characteristics of anomalous GCs. The CN distribution of NGC3201 is quadrimodal, which is more common in anomalous clusters. However, NGC3201 does not belong to the trend of anomalous GCs in the mass-size relation. NGC3201 shows signs that it can be chemically tagged as anomalous: unusual CN-CH relation, indications that pec-S1-S2 is an increasing sequence of C+N+O or s-process element abundances, and a multimodal CN distribution that seems to correlate with s-process element abundances. The differences are: it has a debatable Fe-spread and it does not follow the trend of mass-size of all anomalous clusters. Three scenarios are postulated here: (i) if the sequence pec-S1-S2 has increasing C+N+O and s-process element abundances, NGC3201 would be the first anomalous GC out of the mass-size relation; (ii) if the abundances are almost constant, NGC3201 would be the first non-anomalous GC with multiple CN-CH anti-correlation groups, or (iii) it would be the first anomalous GC without variations in C+N+O and s-process element abundances. In all cases, the definition of anomalous clusters and the scenario where they have an extragalactic origin must be revised. Description: Spectroscopic indices for 28 good quality member RGB stars of the globular cluster NGC3201. For each star, we list star ID, equatorial coordinates, colour, magnitude, heliocentric velocity, signal-to-noise, and spectroscopic indices Fe4382, S(3839), and G4300. We also present the differential indices deltaS(3839) and deltaG4300. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 116 28 Identification of cluster stars, colour, magnitude, velocity, and spectroscopic indices
See also: J/A+A/497/371 : UBVI photometry of NGC 3201 (Kravtsov+, 2009) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Star Star identification 16- 17 I2 h RAh Right ascension (J2000.0) 19- 20 I2 min RAm Right ascension (J2000.0) 22- 27 F6.3 s RAs Right ascension (J2000.0) 29 A1 --- DE- Declination sign (J2000.0) 30- 31 I2 deg DEd Declination (J2000.0) 33- 34 I2 arcmin DEm Declination (J2000.0) 36- 41 F6.3 arcsec DEs Declination (J2000.0) 43- 48 F6.3 mag Vmag V magnitude (1) 50- 54 F5.3 mag B-V B-V colour index (1) 56- 58 I3 km/s HV Heliocentric velocity 60- 64 F5.3 0.1nm Fe4383 Fe4383 spectroscopic index 66- 71 F6.2 --- SNCN S/N at CN index 73- 77 F5.1 --- SNCH S/N at CH index 79- 84 F6.3 mag CN S(3839) spectroscopic index 86- 90 F5.3 mag e_CN Error in S(3839) spectroscopic index 92- 96 F5.3 mag CH G4300 spectroscopic index 98-102 F5.3 mag e_CH Error in G4300 spectroscopic index 104-109 F6.3 mag dCN Differential S(3839) spectroscopic index 111-116 F6.3 mag dCH Differential G4300 spectroscopic index
Note (1): magnitudes and colours are from Kravtsov et al. (2009A&A...497..371K, Cat. J/A+A/497/371).
Acknowledgements: Bruno Dias, bdias(at)eso.org
(End) Bruno Dias [ESO, Chile], Patricia Vannier [CDS] 12-Mar-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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