A Triple Main Sequence in the Globular Cluster NGC 2808

By G. Piotto, L. Bedin, Joseph M. Anderson, I. King, Santi Cassisi, A. Milone, S. Villanova, Adriano Pietrinferni, A. Renzini. 2007

580 citations recorded by the source corpus.

Accurate photometry with HST's ACS shows that the main sequence (MS) of the globular cluster NGC 2808 splits into three separate branches. The three MS branches may be associated with the complexities of the cluster's horizontal branch and of its abundance distribution. We attribute the MS branches to successive rounds of star formation, with different helium abundances; we discuss possible sources of helium enrichment. Some other massive globulars also appear to have complex populations; we compare them with NGC 2808.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/863c1fff8d85e98e7731cbff66a1e4aed21b5371

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. C. Conroy
2. R. Gratton
3. E. Carretta
4. A. Bragaglia
5. A. Renzini
6. Jay Anderson
7. Aaron Dotter
8. G. Piotto

In Instrumentation

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

Citations in the corpus

• 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, methodology): “Given the compelling evidence that NGC 2808 contains stars with different helium abun- dances (perhaps up to Y = 0.40, see Piotto et al. 2007), it is perhaps not surprising that isochrones for Y = 0.25 require an especially large blueward color correction in order to match the turnoff color of this…”
• Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, background): “Piotto et al. (2007) have shown that the MS of NGC 2808 is actually made up of three different sequences: a normal MS, a population with somewhat enriched helium (Y∼ 0.30) and a very helium-rich one (Y∼0.35–0.40).”
• The Double Subgiant Branch of NGC 1851: The Role of the CNO Abundance (2007, background): “More remarkable, from the point of view of studying “normal” GCs, is the recent detection of a triple MS in NGC 2808 (Piotto et al. 2007).”
• THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. IX. HORIZONTAL BRANCH MORPHOLOGY AND THE SECOND PARAMETER PHENOMENON (2009, background): “The presence of more than one stellar population makes a single age determination insufficient to characterize the GC. Ages were not determined for the following GCs: NGC 1851 (Milone et al. 2008, Paper III), NGC 2808 (Piotto et al. 2007), NGC 6388, NGC 6441,12 and NGC 6656 (Piotto 2009).”
• THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. I. OVERVIEW OF THE PROJECT AND DETECTION OF MULTIPLE STELLAR POPULATIONS (2014, background): “For large He differences among the different populations, even these few parallel observations will allow us to detect split MSs, as was successfully done in the cas of NGC 2808 (Piotto et al. 2007).”
• Spectroscopic and photometric evidence of two stellar populations in the Galactic globular cluster NGC 6121 (M 4) (2008, background): “Piotto et al. (2007) simply found them in the form of a MS split.”
• Multiple Stellar Populations in Three Rich Large Magellanic Cloud Star Clusters (2008, background): “NGC 2808 possesses a triple main sequence split, suggesting two helium-enriched populations (Piotto et al. 2007); while NGC 1851 and NGC 6388 show clear splits in their SGBs, possibly indicative of populations with ages ∼ 1 Gyr apart, or of sizeable intracluster variations in chemical composition…”
• Multiple populations in globular clusters (2012, methodology): “…(Y > 0.35) probably required to explain the blue MS of ω Cen and NGC 2808 (Bedin et al. 2004; Norris 2004; Piotto et al. 2005; D’Antona et al. 2005; Piotto et al. 2007), it is difficult to produce Y > 0.35 with AGB stars, although values up to Y ∼ 0.38 can be possibly produced by super-AGB…”
• A stellar census in globular clusters with MUSE: multiple populations chemistry in NGC 2808 (2019, background): “…branches (SGBs), and red giant branches (RGBs) of several clusters and are mainly caused by variations in the strength of molecular bands, such as CN and NH, that affect the stellar flux in the UV and blue optical regions (see, e.g., Piotto et al. 2007, 2012; Milone et al. 2008; Han et al. 2009).”
• Abundance patterns of multiple populations in globular clusters: a chemical evolution model based on yields from AGB ejecta (2010, background): “…clusters (ω Cen and NGC 2808) were recognized to have a large fraction of main sequence stars (∼25% in ω Cen , ∼15% in NGC 2808) in a “blue MS” which could only be interpreted as a very helium rich MS (Bedin et al. 2004; Norris 2004; Piotto et al. 2005; D’Antona et al. 2005; Piotto et al. 2007) 1.”
• THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. VII. RELATIVE AGES (2008, background): “For clusters with multiple stellar populations, such as NGC 1851 (Milone et al. 2008a), NGC 2808 (Piotto et al. 2007), M54 (Siegel et al. 2007) and ωCen (Lee et al. 1999; Pancino et al. 2000; Bedin et al. 2004), the mean ridge line fitting procedure fits the dominant population (see Figure 1).”
• Na-O anticorrelation and HB - VIII. Proton-capture elements and metallicities in 17 globular clusters from UVES spectra (2009, background): “Furthermore, it is the onlycluster where multiple main sequences of quite different He content (Piotto et al. 2007) have been identified so far (beside the peculiar case ofωCen, with its multi-peaked metallicity distribution, see Piotto et al. 2005).”
• A WFC3/HST VIEW OF THE THREE STELLAR POPULATIONS IN THE GLOBULAR CLUSTER NGC 6752 (2013, methodology): “…several GCs host multiple main sequences (MSs) including ω Centauri, NGC2808, 47 Tuc, NGC6752, and NGC6397 (Anderson 1997, Bedin et al. 2004, Piotto et al. 2007, Milone et al. 2010, 2012a,b), which have been associated with stellar populations with different helium abundances (D’Antona &…”
• 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): “Detections of multiple main sequences and giant branches in globular clusters (GC; e.g. ωCen, NGC 2808, and NGC 1851; Bedin et al. 2004(9), Piotto et al. 2007(72), Han et al. 2009(42)) have challenged the notion that these objects are uniformly mono-metallic stellar systems of unique age.”
• The second and third parameters of the horizontal branch in globular clusters (2010, background): “For instance, in the case of NGC 2808, Piotto et al. (2007) found a spread of∼ 0.1 mag in theF475W − F814W colour from very high quality ACS data.”
• The fraction of second generation stars in globular clusters from the analysis of the horizontal branch (2008, methodology): “…bimodality in NGC 2808 was the main hint used by D’Antona & Caloi (2004) to infer the presence of multiple stellar generations differing in Y in the cluster, an interpretation nicely supported by the subsequent observation of the main sequence splitting (D’Antona et al. 2005; Piotto et al. 2007).”
• Scaled solar tracks and isochrones in a large region of the Z-Y plane. II. From 2.5 to 20 solar masses (2009, background): “This assumption is inaccurate for old globular clusters, some of which contain multiple stellar populations with evidence of significant helium enrichment (Piotto et al. 2007; Piotto 2009).”
• A double stellar generation in the globular cluster NGC 6656 (M 22): Two stellar groups with different iron and s-process element abundances (2009, methodology): “Article published by EDP Sciences NGC 2808 was the second (in time) cluster in which a MS divided into three branches was found (Piotto et al. 2007).”
• Massive binaries as the source of abundance anomalies in globular clusters (2009, background): “However, it has recently become clear that many clusters show multiple main sequences and sub giant branches and extended horizontal branches (e.g. Piotto et al. 2007), implying theexistence of multiple populations within one cluster.”
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) (2007, unknown): “…of globular cluster formation is undergoing a revolution since the discovery of the commonality of multiple populations in these systems (e.g., Piotto et al. 2007; Milone et al. 2008; Gratton, Carretta & Bragaglia 2012), which has been established predominantly on the basis of observations…”