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J/AJ/154/155 Abundance variations in the outer halo GC NGC 6229 (Johnson+, 2017)

Light and heavy element abundance variations in the outer halo globular cluster NGC 6229. Johnson C.I., Caldwell N., Rich R.M., Walker M.G. <Astron. J., 154, 155-155 (2017)> =2017AJ....154..155J (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Photometry, infrared ; Radial velocities ; Effective temperatures ; Abundances Keywords: globular clusters: general - globular clusters: individual: NGC 6229 - stars: abundances Abstract: NGC 6229 is a relatively massive outer halo globular cluster that is primarily known for exhibiting a peculiar bimodal horizontal branch morphology. Given the paucity of spectroscopic data on this cluster, we present a detailed chemical composition analysis of 11 red giant branch members based on high resolution (R∼38000), high S/N (>100) spectra obtained with the MMT-Hectochelle instrument. We find the cluster to have a mean heliocentric radial velocity of -138.1-1.0+1.0 km/s, a small dispersion of 3.8-0.7+1.0 km/s, and a relatively low (M/LV)=0.82-0.28+0.49. The cluster is moderately metal-poor with <[Fe/H]≥-1.13 dex and a modest dispersion of 0.06 dex. However, 18% (2/11) of the stars in our sample have strongly enhanced [La,Nd/Fe] ratios that are correlated with a small (∼0.05 dex) increase in [Fe/H]. NGC 6229 shares several chemical signatures with M75, NGC 1851, and the intermediate metallicity populations of ω Cen, which lead us to conclude that NGC 6229 is a lower mass iron-complex cluster. The light elements exhibit the classical (anti-)correlations that extend up to Si, but the cluster possesses a large gap in the O-Na plane that separates first and second generation stars. NGC 6229 also has unusually low [Na,Al/Fe] abundances that are consistent with an accretion origin. A comparison with M54 and other Sagittarius clusters suggests that NGC 6229 could also be the remnant core of a former dwarf spheroidal galaxy. Description: The spectroscopic data for this project were obtained with the MMT 6.5 m telescope instrumented with the Hectochelle multi-fiber spectrograph (Szentgyorgyi et al. 2011PASP..123.1188S) in clear weather on 2016 January 30 and 2016 April 22-30. We utilized the "Cu28" (11 hr), "CJ26" (7 hr), and "OB24" (8 hr) filters to obtain high resolution (R∼38000), high signal-to-noise ratio (S/N>100 per reduced pixel) spectra through a series of 1 hr exposures. Using coordinates and photometry from the Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006, Cat. VII/233), we targeted 57 upper red giant branch (RGB) stars spanning ∼0.5'-20' from the cluster center. Objects: ----------------------------------------------- RA (ICRS) DE Designation(s) ----------------------------------------------- 16 46 58.64 +47 31 36.4 NGC 6229 = GCl 47 ----------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 72 57 Star Identifiers, Coordinates, Photometry, and Velocities table2.dat 42 14 Model Atmosphere Parameters table3.dat 39 88 Line List and Adopted Reference Abundances table4.dat 79 14 Chemical Abundances and Uncertainties: Oxygen to Calcium table5.dat 79 14 Chemical Abundances and Uncertainties: Chromium to Neodymium
See also: VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) J/AJ/101/1699 : Photometry in globular cluster NGC 6229 (Carney+, 1991) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1 A1 --- Memb [MN] Cluster membership flag (M=Cluster member, N=Non-member) 3- 18 A16 --- 2MASS 2MASS star name (HHMMSSss+DDMMSSs) 20- 29 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000) 31- 39 F9.6 deg DEdeg Declination in decimal degrees (J2000) 41- 46 F6.3 mag Jmag [12.315/14.893] 2MASS J band magnitude 48- 53 F6.3 mag Hmag [11.463/14.527] 2MASS H band magnitude 55- 60 F6.3 mag Ksmag [11.283/14.158] 2MASS Ks band magnitude 62- 67 F6.1 km/s HRV [-162.7/7.9] Heliocentric radial velocity 69- 72 F4.1 km/s e_HRV [0.2/33.3] Uncertainty in HRV
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 16 A16 --- 2MASS 2MASS star name (HHMMSSss+DDMMSSs) 18- 21 I4 K Teff [3925/4450]? Effective temperature 23- 26 F4.2 [cm/s2] logg [0.7/1.6]? Surface gravity (in cgs units) 28- 32 F5.2 [-] [Fe/H] [-1.23/-1.04]? Metallicity (in dex) 34- 37 F4.2 [-] e_[Fe/H] [0.04/0.05]? Uncertainty in [Fe/H] 39- 42 F4.2 km/s ksi [1.4/2.2]? Microturbulence velocity ξmic
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 7 F7.2 0.1nm lambda [5731.76/6862.48] Wavelength (Å) 9- 13 A5 --- Species Species identifier 15- 18 F4.2 eV EP [0/5.86] Lower excitation potential 20- 25 F6.3 [-] log(gf) [-9.75/-0.183]? Log of the oscillator strength 27- 29 A3 --- n_log(gf) [hfs ] Note on log(gf) (1) 31- 34 F4.2 [-] logEsun [1.13/8.69] Adopted solar abundance logε(X) (in dex) 36- 39 F4.2 [-] logeEarc [0.57/8.63] Adopted Arcturus abundance logε(X)Arcturus (in dex)
Note (1): Note as follows: hfs = We adopted the hyperfine structure and isotope line lists of Cunha et al. (2002AJ....124..379C) and Lawler et al. (2001ApJ...556..452L) for Cu I and La II, respectively.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 16 A16 --- 2MASS 2MASS star name (HHMMSSss+DDMMSSs) 18- 22 F5.2 [-] [O/Fe] [-0.11/0.71]? [O/Fe] abundance (in dex) 24- 27 F4.2 [-] e_[O/Fe] [0.07]? Uncertainty in [O/Fe] (in dex) 29- 33 F5.2 [-] [Na/Fe] [-0.58/0.25]? [Na/Fe] abundance (in dex) 35- 38 F4.2 [-] e_[Na/Fe] [0.11]? Uncertainty in [Na/Fe] (in dex) 40- 43 F4.2 [-] [Mg/Fe] [0.05/0.34]? [Mg/Fe] abundance (in dex) 45- 48 F4.2 [-] e_[Mg/Fe] [0.06]? Uncertainty in [Mg/Fe] (in dex) 50- 54 F5.2 [-] [Al/Fe] [-0.45/0.39]? [Al/Fe] abundance (in dex) 56- 59 F4.2 [-] e_[Al/Fe] [0.1]? Uncertainty in [Al/Fe] (in dex) 61- 64 F4.2 [-] [Si/Fe] [0.18/0.38]? [Si/Fe] abundance (in dex) 66- 69 F4.2 [-] e_[Si/Fe] [0.08/0.14]? Uncertainty in [Si/Fe] (in dex) 71- 74 F4.2 [-] [Ca/Fe] [0.06/0.34]? [Ca/Fe] abundance (in dex) 76- 79 F4.2 [-] e_[Ca/Fe] [0.12]? Uncertainty in [Ca/Fe] (in dex)
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 16 A16 --- 2MASS 2MASS star name (HHMMSSss+DDMMSSs) 18- 22 F5.2 [-] [Cr/Fe] [-0.13/0.06]? [Cr/Fe] abundance (in dex) 24- 27 F4.2 [-] e_[Cr/Fe] [0.12/0.14]? Uncertainty in [Cr/Fe] (in dex) 29- 33 F5.2 [-] [Ni/Fe] [-0.19/-0.05]? [Ni/Fe] abundance (in dex) 35- 38 F4.2 [-] e_[Ni/Fe] [0.03/0.06]? Uncertainty in [Ni/Fe] (in dex) 40- 44 F5.2 [-] [Cu/Fe] [-0.53/-0.39]? [Cu/Fe] abundance (in dex) 46- 49 F4.2 [-] e_[Cu/Fe] [0.09]? Uncertainty in [Cu/Fe] (in dex) 51- 54 F4.2 [-] [Zr/Fe] [0.21/0.87]? [Zr/Fe] abundance (in dex) 56- 59 F4.2 [-] e_[Zr/Fe] [0.12/0.17]? Uncertainty in [Zr/Fe] (in dex) 61- 64 F4.2 [-] [La/Fe] [0.22/0.99]? [La/Fe] abundance (in dex) 66- 69 F4.2 [-] e_[La/Fe] [0.05/0.08]? Uncertainty in [La/Fe] (in dex) 71- 74 F4.2 [-] [Nd/Fe] [0.2/0.86]? [Nd/Fe] abundance (in dex) 76- 79 F4.2 [-] e_[Nd/Fe] [0.05/0.14]? Uncertainty in [Nd/Fe] (in dex)
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 11-Jul-2018
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