C and N abundances of main sequence and subgiant branch stars in NGC 1851

Lardo, C.; Milone, A. P.; Marino, A. F.; Mucciarelli, A.; Pancino, E.; Zoccali, M.; Carrera, R.; Gonzalez, O. A.

doi:10.1051/0004-6361/201118763

Cited by 46 publications

(76 citation statements)

References 79 publications

(198 reference statements)

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“…They measured C and N (but not O) in subgiant branch stars in NGC 1851 and found that the fainter subgiant branch had a higher C+N content than the brighter subgiant branch, 7.64 ± 0.24 and 7.23 ± 0.31, respectively. Given that the fainter subgiant branch connects to the anomalous RGB, our C+N values for the anomalous (8.45 ± 0.14) and canonical (7.52 ± 0.21) RGBs are qualitatively consistent with Lardo et al (2012), although we note that they used different diagnostics to measure N abundances compared to this study.…”

Section: Ngc 1851supporting

confidence: 73%

“…Therefore any conclusions we draw concerning the CNO content of subgiant branch stars in NGC 1851 will necessarily assume that the abundances we derive for RGB objects would be similar to those on the subgiant branch. That said, we can compare our average abundances for the two RGBs to measurements of subgiant branch stars by Lardo et al (2012). They measured C and N (but not O) in subgiant branch stars in NGC 1851 and found that the fainter subgiant branch had a higher C+N content than the brighter subgiant branch, 7.64 ± 0.24 and 7.23 ± 0.31, respectively.…”

Section: Ngc 1851mentioning

confidence: 87%

“…In the case of NGC 1851, the double subgiant branch ) could be composed of two coeval populations with different mixtures of C+N+O abundances (Cassisi et al 2008). Since the discovery of the double subgiant branch in NGC 1851, understanding its nature and formation history has been an active area of research Han et al 2009;Lee et al 2009;Milone et al 2009;Olszewski et al 2009;Ventura et al 2009;Zoccali et al 2009;Carretta et al 2011Carretta et al , 2012Bekki & Yong 2012;Gratton et al 2012c,b;Lardo et al 2012;Joo & Lee 2013;Marino et al 2014). Indeed, it has been suggested that NGC 1851 may be the product of the merger of two clusters (Carretta et al 2010b).…”

Section: Introductionmentioning

confidence: 99%

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CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Yong¹,

Grundahl²,

Norris³

2014

Monthly Notices of the Royal Astronomical Society

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We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O) = 8.16 ± 0.10 (σ = 0.34) and 7.62 ± 0.02 (σ = 0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of four (∼0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances.

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Section: Ngc 1851supporting

confidence: 73%

Section: Ngc 1851mentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Yong¹,

Grundahl²,

Norris³

2014

Monthly Notices of the Royal Astronomical Society

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“…It is difficult to imagine that this could lead to a double-peaked distribution like the one observed by Marino et al (2008) in M4. We are able to explain the more uniform distribution found in NGC 1851, however (Lardo et al 2012). Details of abundance distributions will be the subject of future work.…”

Section: The Distribution Of Orbit Eccentricities and The Ratio Of Prmentioning

confidence: 74%

Superbubble dynamics in globular cluster infancy

Krause

Charbonnel

Decressin

et al. 2013

A&A

135

155

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Context. The self-enrichment scenario for globular clusters (GC) requires large amounts of residual gas after the initial formation of the first stellar generation. Recently, we found that supernovae may not be able to expel that gas, as required to explain their presentday gas-free state, and suggested that a sudden accretion onto the dark remnants at a stage when type II supernovae have ceased may plausibly lead to fast gas expulsion. Aims. Here, we explore the consequences of these results for the self-enrichment scenario via fast-rotating massive stars (FRMS). Methods. We analysed the interaction of FRMS with the intra-cluster medium (ICM), in particular where, when, and how the second generation of stars may form. From the results, we developed a timeline of the first ≈40 Myr of GC evolution. Results. Our previous results imply three phases during which the ICM is in a fundamentally different state, namely the wind bubble phase (lasting 3.5 to 8.8 Myr), the supernova phase (lasting 26.2 to 31.5 Myr), and the dark remnant accretion phase (lasting 0.1 to 4 Myr): (i) Quickly after the first-generation massive stars have formed, stellar wind bubbles compress the ICM into thin filaments. No stars may form in the normal way during this phase because of the high Lyman-Werner flux density. If the first-generation massive stars have equatorial ejections however, as we proposed in the FRMS scenario, accretion may resume in the shadow of the equatorial ejecta. The second-generation stars may then form due to gravitational instability in these disc, which are fed by both the FRMS ejecta and pristine gas. (ii) In the supernova phase the ICM develops strong turbulence, with characteristic velocities below the escape velocity. The gas does not accrete either onto the stars or onto the dark remnants in this phase because of the high gas velocities. The strong mass loss associated with the transformation of the FRMS into dark remnants then leads to the removal of the secondgeneration stars from the immediate vicinity of the dark remnants. (iii) When the supernovae have ceased, turbulence quickly decays, and the gas can once more accrete, now onto the dark remnants. As discussed previously, this may release sufficient energy to unbind the gas, and may happen fast enough so that a large fraction of less tightly bound first-generation stars are lost. Conclusions. Studying the FRMS scenario for the self-enrichment of GCs in detail reveals the important role of the physics of the ICM for our understanding of the formation and early evolution of GCs. Depending on the level of mass segregation, this sets constraints on the orbital properties of the stars, in particular high orbital eccentricities, which likely has implications on the GC formation scenario.

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“…This has been observed in most, if not all, clusters. With the recent interest in NGC 1851 there have been a couple of studies of CN, on the MS (Pancino et al 2010) and the two SGBs (Lardo et al 2012). There does, however, appear to be a dearth of studies of CN in giants in NGC 1851-here we report on observations focusing on CN band strengths in the RGB and asymptotic giant branch (AGB) stars of NGC 1851.…”

Section: Introductionmentioning

confidence: 99%

Cyanogen in NGC 1851 Red Giant Branch and Asymptotic Giant Branch Stars: Quadrimodal Distributions

Campbell¹,

Yong

Boer

et al. 2012

ApJ

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The Galactic globular cluster NGC 1851 has raised much interest since Hubble Space Telescope photometry revealed that it hosts a double subgiant branch. Here we report on our homogeneous study into the cyanogen (CN) band strengths in the red giant branch (RGB) population (17 stars) and asymptotic giant branch (AGB) population (21 stars) using AAOmega/2dF spectra with R ∼ 3000. We discover that NGC 1851 hosts a quadrimodal distribution of CN band strengths in its RGB and AGB populations. This result supports the merger formation scenario proposed for this cluster, such that the CN quadrimodality could be explained by the superposition of two "normal" bimodal populations. A small sample overlap with an abundance catalog allowed us to tentatively explore the relationship between our CN populations and a range of elemental abundances. We found a striking correlation between CN and [O/Na]. We also found that the four CN peaks may be paired-the two CN-weaker populations being associated with low Ba and the two CN-stronger populations with high Ba. If true, then s-process abundances would be a good diagnostic for disentangling the two original clusters in the merger scenario. More observations are needed to confirm the quadrimodality and also the relationship between the subpopulations. We also report CN results for NGC 288 as a comparison. Our relatively large samples of AGB stars show that both clusters have a bias toward CN-weak AGB populations.

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C and N abundances of main sequence and subgiant branch stars in NGC 1851

Cited by 46 publications

References 79 publications

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Superbubble dynamics in globular cluster infancy

Cyanogen in NGC 1851 Red Giant Branch and Asymptotic Giant Branch Stars: Quadrimodal Distributions

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