Na-O anticorrelation and HB. I. The Na-O anticorrelation in NGC 2808

By E. Carretta, A. Bragaglia, R. Gratton, F. Leone, A. Recio-Blanco, S. L. I. Bologna, Inaf - Padova, Inaf - Catania, Observatoire Cote d'Azur. 2005

157 citations recorded by the source corpus.

We derived the atmospheric parameters and elemental abundances of Fe, O, and Na for about 120 red giant stars in the Galactic globular cluster NGC 2808. Our results are based on the analysis of medium-high resolution (R = 22 000−24 000) GIRAFFE spectra acquired with the FLAMES spectrograph at VLT-UT2 as a part of a project aimed at studying the Na-O anticorrelation as a function of physical parameters in globular clusters. We present the anticorrelation of Na and O abundances in NGC 2808 here, and discuss the distribution function of stars along this relation. Besides a bulk of O-normal stars with the typical composition of field halo stars, NGC 2808 seems to host two other groups of O-poor and super O-poor stars. In this regard, NGC 2808 is similar to M 13, the template cluster for the Na-O anticorrelation. However, in contrast to M 13, most stars in NGC 2808 are O-rich. This might be related to the horizontal branch morphologies that are very different in these two clusters. The average metallicity we found for NGC 2808 is [Fe/H] = −1.10 (rms = 0.065 dex, from 123 stars). We also found some evidence of a small intrinsic spread in metallicity, but more definitive conclusions are hampered by the presence of a small differential reddening.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1d8cd28a172370ddc69de4fa0409a99f9c461c24

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In Astronomy and Astrophysics

1. R. Gratton
2. A. Bragaglia
3. E. Carretta
4. F. D’Antona
5. Jay Anderson
6. A. Renzini
7. G. Piotto
8. A. Milone

In Instrumentation

1. R. Gratton
2. E. Carretta
3. A. Bragaglia
4. F. D’Antona
5. G. Piotto
6. Jay Anderson
7. A. Milone
8. L. Bedin

Citations in the corpus

• The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – IX. The Atlas of multiple stellar populations (2016, methodology): “In Papers II and III we performed a similar chemical tagging for NGC 7089 and for NGC 2808, by comparing the chromosome map of these clusters with the light-element abundances from Yong et al. (2014) and Carretta et al. (2006), respectively.”
• The SUMO project: a SUrvey of Multiple pOpulations in globular clusters (2013, background): “Furthermore, spectroscopic studies of RGB, HB, and bright MS stars have revealed significant star-to-star differences in the light-element abundances and an extended Na-O anticorrelation (Norris 1981; Carretta et al. 2006; Bragaglia et al. 2010).”
• Massive AGB models of low metallicity: the implications for the self-enrichment scenario in metal-poor globular clusters (2009, background): “Columns 3 to 8 of Table 2 contain the average abundance ratios of the elements mostly investigated in the spectroscopic surveys of GCs, in terms of the quantity [X/Fe]=log(X/Fe) − log(X/Fe)⊙.”
• Origin of multiple stellar populations in globular clusters and their helium enrichment (2008, background): “O anticorrelation, with three distinct peaks in oxygen abundance (Carretta et al. 2006), that are likely to be associated with the three distinct populations revealed by the MS photometry (Piotto et al. 2007).”
• Multiple populations in globular clusters (2012, methodology): “2005a); NGC 2808 (Carretta et al. 2006); NGC 6218 (Johnson et al.”
• Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682) (2009, background): “In particular,in October 5, 2009 16 E. Pancino et al.: Abundances of five Open Clusters the [O/Fe]–[Na/Fe] plane, all 15 stars roughly occupy the solar region around zero that in Figure 5 by Carretta et al. (2006) contains normal stars only (see also De Silva et al., 2009).”
• N-body modelling of globular clusters: masses, mass-to-light ratios and intermediate-mass black holes (2016, unknown): “…IFU D’Orazi et al. (2015) LOS NGC 2419 Baumgardt et al. (2009) LOS Ibata et al. (2011) LOS Bellazzini (2007) SD NGC 2808 Cacciari et al. (2004) LOS Carretta et al. (2006) LOS Gratton et al. (2011) LOS Lützgendorf et al. (2012) IFU, LOS Marino et al. (2014) LOS Lardo et al. (2015) LOS…”
• Abundance patterns of multiple populations in globular clusters: a chemical evolution model based on yields from AGB ejecta (2010, background): “No iron abundance difference is present in these populations, but they show an extended [O/Fe]-[Na/Fe] anticorrelation (Carretta et al. 2006).”
• A stellar census in globular clusters with MUSE: multiple populations chemistry in NGC 2808 (2019, methodology): “Studies on the abundances of RGB stars in globular clusters have mostly been performed using high resolution (R∼ 20 000−40 000) spectra (see, e.g., Carretta et al. 2006 and following papers in that series).”
• MULTIPLE STELLAR POPULATIONS IN 47 Tucanae (2011, background): “According to this picture, the triple MS in NGC 2808 can also correspond to the three groups of stars with different oxygen and sodium abundances observed among the RGB stars (Carretta et al. 2006), likely to come from three successive episodes of star formation.”
• Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, background): “This survey (see Carretta et al. 2006a, hereafter Paper I) aims toprovide significant constraints and answers to fundamental questions such as:(i) Were GC stars really born in a single ”instantaneous” burst?”
• Spectroscopic and photometric evidence of two stellar populations in the Galactic globular cluster NGC 6121 (M 4) (2008, methodology): “It is noteworthy to recognize her that the Na-O anticorrelation has been found in about 20 GCs (see Carretta et al. 2006 for the most updated list).”
• Properties of stellar generations in globular clusters and relations with global parameters (2010, background): “Before starting our present discussion, we summarise the results of our project “Na-O anticorrelation and HB” (Carretta et al. 2006).”
• Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, background): “O anomalies (e.g. Carretta et al. 2006), lead us to conclude that, in the clusters so far examined, the percentage of stars of the SG is generally ∼40–60% (D’Antona & Caloi 2008).”
• Intrinsic iron spread and a new metallicity scale for globular clusters (2009, methodology): “The data analysis has already been described in detail elsewhere (Carretta et al. 2006, 2007a−c; Gratton et al. 2006, 2007; Carretta et al. 2009a,b) and will not be repeated here.”
• On the self-enrichment scenario of galactic globular clusters: constraints on the IMF (2006, background): “The data of Carretta et al. (2006) for the 91 stars where both O and Na are detected, are displayed in Fig.”