The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851

By A. Milone, L. Bedin, G. Piotto, Jay Anderson, I. King, A. Sarajedini, Aaron Dotter, B. Chaboyer, A. Marín-Franch, S. Majewski and 6 more. 2007

248 citations recorded by the source corpus.

Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) reveals that the subgiant branch (SGB) of the globular cluster NGC 1851 splits into two well-defined branches. If the split is due only to an age effect, the two SGBs would imply two star formation episodes separated by ~1 Gyr. We discuss other anomalies in NGC 1851 that could be interpreted in terms of a double stellar population. Finally, we compare the case of NGC 1851 with the other two globulars known to host multiple stellar populations, and show that all three clusters differ in several important respects.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6ec196e13a629e4e955bdf68d10b86bd96250970

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In Astronomy and Astrophysics

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

In Instrumentation

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

Citations in the corpus

• The fraction of second generation stars in globular clusters from the analysis of the horizontal branch (2008, background): “3.2) whose HR diagram shows a splitting in the subgiant branch (Milone et al. 2008).”
• A double stellar generation in the globular cluster NGC 6656 (M 22): Two stellar groups with different iron and s-process element abundances (2009, background): “There is also some evidence of two groups of stars of different s-process element content, as well as of two groups of stars with different CN-strengths, that are possibly related to the two sequences photometrically identified by Milone et al. (2008) along the SGB.”
• Spectroscopic and photometric evidence of two stellar populations in the Galactic globular cluster NGC 6121 (M 4) (2008, background): “RGB populations is along the HB. Milone et al. (2008) suggest that the bimodal HB of NGC 1851 can be interpreted in terms of the presence of two distinct stellar populations in this cluster, and tentatively link the bright SGB to the red HB (RHB) and the fainter SGB to the blue HB (BHB).”
• 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): “In addition, new HST photometric data (Milone et al. 2008) have revealed a split subgiant branch.”
• Multiple Stellar Populations in Three Rich Large Magellanic Cloud Star Clusters (2008, background): “…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 (Milone et al. 2008; Piotto 2008; Salaris et al. 2008).”
• MULTIPLE STELLAR POPULATIONS IN 47 Tucanae (2011, background): “…Tuc; NGC 104), and NGC 6752 (Piotto et al. 2007; Anderson et al. 2009; Milone et al. 2010), while splits in the subgiant branches (SGBs) have been detected in NGC 1851, NGC 6656 (M22), 47 Tuc, and at least five other GCs (Milone et al. 2008; Marino et al. 2009; Anderson et al. 2009; Piotto 2009).”
• The two metallicity groups of the globular cluster M 22: a chemical perspective (2011, background): “…of multiple stellar populations has been recently observed in many GCs in the form of multiple main sequences (Bedin et al. 2004, Piotto et al. 2007, Anderson et al. 2009, and Milone et al. 2010), split sub-giant branches (Milone et al. 2008, and Piotto 2009), and multiple red- ar X iv :1 10 5.”
• Formation and dynamical evolution of multiple stellar generations in globular clusters (2008, background): “…and it is present only 2 A different, borderline, situation seems to be present in NGC 1851, whose HR diagram shows a splitting of the subgiant branch (Milone et al. 2008), that can be interpreted as due to two different stellar populations differing in total CNO abundance (Cassisi et al. 2008).”
• The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters – IX. The Atlas of multiple stellar populations (2016, background): “…that the split SGB of NGC 1851 is real, but also show that the faint SGB is visible also in CMDs made with optical filters, like mF606W vs.mF606W− mF814W, where stellar colors and luminosities are not significantly affected by light-element abundance variations (see also Milone et al. 2008).”
• The SUMO project: a SUrvey of Multiple pOpulations in globular clusters (2013, background): “1999; Marino et al. 2008; Yong & Grundahl 2008; Lee et al. 2009), and in some cases of a sub-giant branch (SGB) splittings (e.g. Milone et al. 2008; Marino et al. 2009; Piotto et al. 2012).”
• Photometric signatures of multiple stellar populations in galactic globular clusters (2011, methodology): “It has to be noted that Han et al. (2009) could not detect any SGB split in the MV vs. V-I CMD, probably due to the lower quality of their ground-based photometry compared to the HST-based on in Milone et al. (2008).”
• 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): “In the case of NGC 1851, the double subgiant branch discovered by Milone et al. (2008) is clearly present in our data and we have fitted isochrones to the dominant, brighter population (although this is not apparent at the scale of the plot in the top right-hand corner).”
• 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).”
• The second and third parameters of the horizontal branch in globular clusters (2010, methodology): “SGB splitting measured using visual-red-near infrared colours (see e.g., Milone et al. 2008) might be due to a variation either in age or most likely total CNO content (see e.g., D’Antona et al. 2009 and Cassisi et al. 2008), or even [Fe/H] (in this case however some spread in the MS and RGB is…”
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) (2007, unknown): “…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 collected from the…”
• Multiple stellar populations in Magellanic Cloud clusters - I. An ordinary feature for intermediate age globulars in the LMC? (2008, methodology): “Interestingly enough, a similar population ratio between the bright and the faint SGB ratios has been found in the Galactic globular clusters NGC 1851 (Milone et al. 2008a) and NGC 6388 (Piotto et al., in preparation).”