On the self-enrichment scenario of galactic globular clusters: constraints on the IMF

By N. Prantzos, C. Charbonnel, Corinne Charbonnel Institut d'Astrophysique de Paris, Geneva Observatory Lat Toulouse. 2006

188 citations recorded by the source corpus.

Aims. Galactic globular cluster (GC) stars exhibit abundance patterns that are not shared by their field counterparts, e.g. the welldocumented O-Na and Mg-Al anticorrelations. Recent spectroscopic observations of GC turnoff stars have provided compelling evidence that these abundance anomalies were already present in the gas from which the observed stars formed. A widely held hypothesis is that the gas was “polluted” by stars that were more massive (and evolving faster) than the presently observed low-mass stars. In the framework of this “self-enrichment” scenario for GCs, we present a new method of deriving the initial mass function (IMF) of the polluters, by using the O/Na abundance distribution. Methods. We focus on NGC 2808, a GC for which the largest sample of O and Na abundance determinations is presently available. We use the abundance distribution of [O/Na] to derive the amount of polluted material with respect to the original composition. We explore two scenarios in detail for the self-enrichment of the cluster, which differ by the assumptions made on the composition of the polluter ejecta. In each case we consider two classes of possible “culprits”: massive asymptotic giant branch (AGB) stars (4−9 M� ) and winds of massive stars (WMS) in the mass range 10−100 M� . Results. We obtain upper limits for the slope of the IMF (assumed to be given by a power-law) of the stars initially more massive than the present turnoff mass. We also derive lower limits for the amount of stellar residues in NGC 2808. Conclusions. We find that the polluter IMF had to be much flatter than the presently observed IMFs in stellar clusters, which agrees with the results of two other GC IMF determination methods, which we also discuss. Likewise, we find that the present mass of the GC should be totally dominated by stellar remnants if the polluters were AGB stars, which is not the case if the culprits are WMS. We critically analyse the advantages and shortcomings of each potential polluter class and find the WMS scenario more attractive.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/875514a1bef78802834885eab3c1c986474637eb

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Citations in the corpus

The second and third parameters of the horizontal branch in globular clusters (2010, methodology): “A similar dilution model has been successfully used to explain many features of the Na-O anti-correlation (see discussion in Prantzos & Charbonnel 2006), including its shape and the residual observed Li abundances in stars severely depleted in O in NGC 6752 (Pasquini et al. 2005).”
From star clusters to dwarf galaxies: the properties of dynamically hot stellar systems (2008, background): “Especially a top-heavy IMF seems attractive, since it is also suggested by models for galaxy evolution (e.g. Baugh et al. 2005; Nagashima et al. 2005; van Dokkum 2007) or GC evolution (e.g. D’Antona & Caloi 2004; Prantzos & Charbonnel 2006).”
Signatures of intrinsic Li depletion and Li-Na anti-correlation in the metal-poor globular cluster NGC 6397 , (2009, methodology): “…of the self-enrichment scenario the Li content of globular-cluster stars is actually an important tool to quantify the dilution factor between the ejecta of the massive stars responsible for pollution and the pristine intracluster matter (Prantzos & Charbonnel 2006; Decressin et al. 2007b,a).”
Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-A (2008, background): “Among them we recall Karakas et al. (2006) on the AGB self-pollution scenario, Maeder & Meynet (2006) on rotating low-metallicity massive stars, while Prantzos and Charbonnel (2006) discuss the drawbacks of both hypotheses.”
Intrinsic iron spread and a new metallicity scale for globular clusters (2009, background): “Star to star abundance variations in these elements are expected to also come with differences in the main outcome of the H burning, the He content (Gratton et al. 2009; Bragaglia et al. in preparation; Prantzos & Charbonnel 2006; Ventura et al. 2001).”
Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, methodology): “3.1)— than today’s GC (D’Antona & Caloi 2004; Bekki & Norris 2006; Prantzos & Charbonnel 2006; D’Antona et al. 2007; Decressin et al. 2007b), or the system evolves at constant mass and the IMF is highly anomalous (D’Antona & Caloi 2004; Decressin et al. 2007b, see also Downing & Sills (2007) for a…”
Multiple populations in globular clusters (2012, background): “…are intermediate-mass AGB (Cottrell & da Costa 1981; D’Antona et al. 1983; Ventura et al. 2001) and/or super-AGB2 stars (Pumo et al. 2008; Ventura & D’Antona 2010, 2011), and fast rotating massive stars (FRMS, Norris 2004; Maeder & Meynet 2006; Prantzos & Charbonnel 2006; Decressin et al. 2007a,b).”
Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters (2006, background): “Prantzos & Charbonnel (2006) proposed a comprehensive (albeit qualitative) scenario for the role of massive stars, suggesting that their winds provide the metal-enriched material for the next stellar generation, and that the subsequent supernova explosions provide the trigger for star formation;…”
Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation (2014, background): “This evidence for top-heavy IMFs in massively star-bursting clusters appears from four entirely independent data sets: (i) the elevated dynamical M/L ratios of UCDs [289,290], (ii) the higher incidence of LMXBs in UCDs [291], (iii) globular clusters in the Milky Way which have “damaged” present-day ”
Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters (2007, background): “…the CNOcycle and the NeNa- and MgAl-chains that occurred in an early generation of more massive and faster evolving globular cluster stars2 (see Prantzos & Charbonnel 2006, hereafter PC06, and 1 On the contrary, the content in heavy elements (i.e., Fe-group, α-elements) is fairly constant from…”
Properties of stellar generations in globular clusters and relations with global parameters (2010, background): “…that the second-generation stars (that presently make up some 2/3 of the Page 9 of 29 stars of a typical GC, see Paper VII) should have formed from the ejecta of only a fraction of the first-generation stars, that actually coincide with the primordial component in GCs (Prantzos & Charbonnel 2006).”
Massive AGB models of low metallicity: the implications for the self-enrichment scenario in metal-poor globular clusters (2009, background): “Either the winds from massive AGBs (Cottrell & Da Costa 1981; Ventura et al. 2001) or those from fast rotating massive stars (Prantzos & Charbonnel 2006) have been proposed as progenitors of the SG; the latter scenario is described in detail in Decressin et al. (2007) and references therein; here…”
Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, background): “Hence, while an overall correlation between Na and Al might be expected (because they should share dilution effects like those considered by Prantzos & Charbonnel 2006), details of this correlation are not obvious and can provide crucial information on the nature of the polluters.”
Young Massive Star Clusters (2010, background): “The two main candidates currently suggested as possible sources of enriched gas for SG formation are rapidly rotating massive stars (Prantzos & Charbonnel 2006, Decressin et al. 2007) and massive (4–9 M⊙) Asymptotic Giant Branch (AGB) stars (Ventura et al. 2001, Karakas & Lattanzio 2007 In order to…”
Massive binaries as the source of abundance anomalies in globular clusters (2009, methodology): “…products (Ventura et al. 2001; D’Antona et al. 2002; Denissenkov & Herwig 2003) and fastrotating massive stars (we refer to these asspin stars), which are believed to expel processed material centrifugally when they reach break-up rotation (Prantzos & Charbonnel 2006; Decressin et al. 2007b).”