Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra

By E. Carretta, A. Bragaglia, R. Gratton, S. Lucatello, G. Catanzaro, F. Leone, M. Bellazzini, R. Claudi, V. D’Orazi, Y. Momany and 5 more. 2009

659 citations recorded by the source corpus.

We present abundances of Fe, Na, and O for 1409 red giant stars in 15 galactic globular clusters (GCs), derived from the homogeneous analysis of high-resolution FLAMES/GIRAFFE spectra. Combining the present data with results from our FLAMES/UVES spectra and from previous studies within the project, we obtained a total sample of 1958 stars in 19 clusters, the largest and most homogeneous database of this kind to date. The programme clusters cover a range in metallicity from [Fe/H] = −2. 4d ex to [Fe/H] = −0.4 dex, with a wide variety of global parameters (morphology of the horizontal branch, mass, concentration, etc.). For all clusters we find the Na-O anticorrelation, the classical signature of the operation of proton-capture reactions in H-burning at high temperature in a previous generation of more massive stars that are now extinct. Using quantitative criteria (from the morphology and extension of the Na-O anticorrelation), we can define three different components of the stellar population in GCs. We separate a primordial component (P) of first-generation stars, and two components of second-generation stars, that we name intermediate (I) and extreme (E) populations from their different chemical composition. The P component is present in all clusters, and its fraction is almost constant at about one third. The I component represents the bulk of the cluster population. On the other hand, E component is not present in all clusters, and it is more conspicuous in some (but not in all) of the most massive clusters. We discuss the fractions and spatial distributions of these components in our sample and in two additional clusters (M 3 = NGC 5272 and M 13 = NGC6205) with large sets of stars analysed in the literature. We also find that the slope of the anti-correlation (defined by the minimum O and maximum Na abundances) changes from cluster-to-cluster, a change that is represented well by a bilinear relation on cluster metallicity and luminosity. This second dependence suggests a correlation between average mass of polluters and cluster mass.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/954406b60af1f0a4be47bcdaa572faac391c4c7b

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In Astronomy and Astrophysics

1. Hans-Walter Rix
2. C. Conroy
3. Jo Bovy
4. Timothy C. Beers
5. R. Gratton
6. E. Carretta
7. A. Bragaglia
8. Jay Anderson

In Instrumentation

1. Hans-Walter Rix
2. C. Conroy
3. R. Gratton
4. E. Carretta
5. A. Bragaglia
6. Jo Bovy
7. F. D’Antona
8. Jay Anderson

Citations in the corpus

• THE SEGUE STELLAR PARAMETER PIPELINE. V. ESTIMATION OF ALPHA-ELEMENT ABUNDANCE RATIOS FROM LOW-RESOLUTION SDSS/SEGUE STELLAR SPECTRA (2010, background): “This statement also holds true for Na and Al, which exhibit star-to-star variations in the GCs (e.g., Carretta et al. 2009a, 2009b; references therein), as the wavelength window for measuring [α/Fe] does not include any strong lines of these two elements.”
• Abundance patterns of multiple populations in globular clusters: a chemical evolution model based on yields from AGB ejecta (2010, methodology): “Carretta et al. (2009a) find that the upper limit to the scatter of iron is less than 0.05 dex in the 19 clusters they examine.”
• Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, methodology): “Both small and massive clusters are included in our sample, and finally all the age classes defined by Zinn, Lee, and collaborators (see e.g. Mackey and van den Bergh 2005) are represented well in the sample (see also Carretta et al. 2009, Paper VII).”
• THE ABUNDANCES OF NEUTRON-CAPTURE SPECIES IN THE VERY METAL-POOR GLOBULAR CLUSTER M15: A UNIFORM ANALYSIS OF RED GIANT BRANCH AND RED HORIZONTAL BRANCH STARS (2011, background): “…behaviors of globulars include star-to-star scatter of light element [el/Fe] ratios (for C, N, O, Na, Mg, and Al) in both main sequence and giant stars (this is in contrast to the abundance trends of halo field stars; e.g. Carretta et al. 2009a(18) and Gratton, Sneden, & Carretta 2004(36))1.”
• THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED METHOD ALONG WITH COLOR–MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES (2013, background): “For example, ages as young as 11 Gyr (di Cecco et al. 2010) or as old as 13.5 Gyr (VandenBerg, Casagrande, & Stetson 2010) have been derived for M 92, which has [Fe/H] ≈ −2.35 (Carretta et al. 2009a, hereafter CBG09).”
• The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – IX. The Atlas of multiple stellar populations (2016, background): “Multiple stellar populations in NGC 6121 have been widely studied, both photometrically (e.g. Marino et al. 2008; Milone et al. 2014; Nardiello et al.2015b) and spectroscopically (e.g. Ivans et al. 1999; Marino et al.2008, 2011; Carretta et al. 2009, 2013).”
• The second and third parameters of the horizontal branch in globular clusters (2010, methodology): “…magnitude diagrams (CMD) and accurate ages provided by ground (Rosenberg et al. 2000a,b) and space observations (e.g., Piotto et al. 2002), and the extensive data on the Na-O anticorrelation from our FLAMES survey (Carretta et al. 2009a,b and references therein), complemented by literature data.”
• CHEMICAL TAGGING CAN WORK: IDENTIFICATION OF STELLAR PHASE-SPACE STRUCTURES PURELY BY CHEMICAL-ABUNDANCE SIMILARITY (2016, background): “Globular clusters famously demonstrate correlations in these elements (for example, Norris & Da Costa 1995; Carretta et al. 2009, and references therein), thereby making them suitable projections for us to show in verifying and examining any substructure identified by k-means (or any other…”
• MULTIPLE STELLAR POPULATIONS IN 47 Tucanae (2011, methodology): “O anticorrelation in RGB stars of 47 Tuc has recently been studied by Carretta et al. (2009b), and their data are shown in Figure 24, where we have made an arbitrary division into Na-poor/O-rich stars (green triangles) and Na-rich/O-poor stars (magenta circles).”
• Chemical similarities between Galactic bulge and local thick disk red giants: O, Na, Mg, Al, Si, Ca, and Ti (2010, neutral): “2005; Carretta et al. 2009).”
• CHEMICAL ABUNDANCES FOR 855 GIANTS IN THE GLOBULAR CLUSTER OMEGA CENTAURI (NGC 5139) (2010, methodology): “Monometallic globular clusters typically consist of ∼20–40% of stars belonging to the primordial component, ∼30–80% in the intermediate component, and .20% in the extreme component (e.g., Carretta et al. 2009a).”
• Properties of stellar generations in globular clusters and relations with global parameters (2010, methodology): “In summary, in this paper we combine the results of our extensive survey of abundances in RGB stars in 19 GCs (Carretta et al. 2009a,b,c) with previous knowledge of a GC, in order to discuss scenarios for their formation.”
• Multiple populations in globular clusters (2012, background): “(2007): the globular clusters must have been initially a large factor (10-100) more massive than today and almost all the first generation stars must have been preferentially lost.”
• THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. I. OVERVIEW OF THE PROJECT AND DETECTION OF MULTIPLE STELLAR POPULATIONS (2014, background): “…that can be ascribed to the proto-galactic interstellar matter out of which theyformed, the second-generation (2G) stars can be depleted in C and O, enhanced in N and Na (e.g., Carretta et al. 2009, Marino et al. 2008, 2011a 2011b, 2012 2014), and enhanced in He (Milone et al. 2012a, 2012b, 2014a).”
• Stellar Population Inference with Prospector (2020, background): “However, globular clusters present unique challenges – at low metallicities they have very prominent blue horizontal branches (BHB), which may be a consequence of the unusual light-element abundance variations that have been detected in nearly all clusters (Carretta et al. 2009).”
• Intrinsic iron spread and a new metallicity scale for globular clusters (2009, methodology): “However, the error would be larger where the two sequences are so close that cannot be distinguished, but separated enough to give a wrong temperature when the luminosity is used, as in the procedure adopted in our analysis (see Carretta et al. 2009a for further details).”