Different sodium enhancements among multiple populations of Milky Way globular clusters

Piatti, Andrés E.

doi:10.1051/0004-6361/202039128

Cited by 5 publications

(4 citation statements)

References 38 publications

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“…Such a cluster origin agrees well with the cluster age (13.97±0.50 Gyr; Valcin et al 2020), its low metal-content ([Fe/H] = -1.99 dex; Marino et al 2019), and the difference in sodium abundance between first and second generation stars. Indeed, Piatti (2020) found that globular clusters with sodium abundance enrichments larger than 0.3 dex hinted at an accreted origin, particularly the oldest globular clusters. NGC 6809 has a sodium abundance enrichment of 0.72 dex (Piatti 2020).…”

Section: Analysis and Discussionmentioning

confidence: 99%

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The surroundings of the Milky Way globular cluster NGC 6809

Piatti

2021

Preprint

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We study the outer regions of the Milky Way globular cluster NGC 6809 based on Dark Energy Camera (DECam) observations, which reach nearly 6 mag below the cluster main sequence (MS) turnoff. In order to unveil its fainter outermost structure, we built stellar density maps using cluster MS stars, once the contamination of field stars was removed from the cluster color-magnitude diagram. We found that only the resulting stellar density map for the lightest stars exhibits some excesses of stars at opposite sides from the cluster centre that diminish soon thereafter at ∼ 0.32 • . Studied globular clusters with apogalactic distances smaller than that of NGC 6809 (5.5 kpc) do not have observed tidal tails. The lack of detection of tidal tails in the studied inner globular cluster sample could be due to the reduced diffusion time of tidal tails by the kinematically chaotic nature of the orbits of these globular clusters, thus shortening the time interval during which the tidal tails can be detected. Further investigations with an enlarged cluster sample are needed to confirm whether chaotic and non-chaotic orbits are responsible for the existence of globular clusters with tidal tails and those with extra-tidal features that are different from tidal tails or without any signatures of extended stellar density profiles.

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Section: Analysis and Discussionmentioning

confidence: 99%

“…Indeed, Piatti (2020) found that globular clusters with sodium abundance enrichments larger than 0.3 dex hinted at an accreted origin, particularly the oldest globular clusters. NGC 6809 has a sodium abundance enrichment of 0.72 dex (Piatti 2020).…”

Section: Analysis and Discussionmentioning

confidence: 99%

The surroundings of the Milky Way globular cluster NGC 6809

Piatti

2021

Preprint

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“…Star clusters have long been extolled as critical test beds of stellar evolution while simultaneously serving as well-defined, individual data points for probing the temporal, chemical, and spatial evolution of the Galaxy owing to the unique distance, age, and chemical composition common to all stars within a cluster (see, e.g., Twarog et al 1997;Friel et al 2002;Netopil et al 2016;Donor et al 2020). While the claim of uniformity for the last two parameters has been successfully challenged by globular clusters exhibiting multigenerational abundance trends (see, e.g., Gratton et al 2004;Carretta et al 2009;Milone et al 2012;Piatti 2020), open clusters still retain the mantle of single-generation parametric homogeneity, apart from abundance variations due to the internal evolution of specific elements like Li or CNO. In particular, in the case of M67, diffusion and rotational mixing have arisen as potential sources of significant multielemental variations with evolutionary phase (Souto et al 2019;Boesgaard et al 2020).…”

Section: Introductionmentioning

confidence: 99%

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

Twarog¹,

Anthony-Twarog²,

Deliyannis³

2023

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Precision CCD uvbyCaHβ photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005–0.020 mag level to V ∼ 17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial velocity information. From single-star members, offsets in the sense (M67−NGC 752) are δ E(b − y) = −0.005 ± 0.001 (sem) mag from 327 F/G dwarfs and δ[Fe/H] = 0.062 ± 0.006 (sem) dex from the combined m 1 and hk indices of 249 F dwarfs, leading to E(b − y) = 0.021 ± 0.004 (sem) and [Fe/H]M67 = +0.030 ± 0.016 (sem) assuming [Fe/H]Hyades = +0.12. With probable binaries eliminated using c 1, (b − y) indices, 83 members with (π/σ π ) > 50 generate (m − M)0 = 8.220 ± 0.005 (sem) for NGC 752 and an isochronal age of 1.45 ± 0.05 Gyr. Using the same parallax restriction for 312 stars, M67 has (m − M) = 9.77 ± 0.02 (sem), leading to an age tied solely to the luminosity of the subgiant branch of 3.70 ± 0.03 Gyr. The turnoff color spread implies ±0.1 Gyr, but the turnoff morphology defines a younger age/higher mass for the stars, consistent with recent binary analysis and broadband photometry indicating possible missing physics in the isochrones. Anomalous stars positioned blueward of the turnoff are discussed.

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“…While the claim of uniformity for the latter two parameters has been successfully challenged by globular clusters exhibiting multigenerational abundance trends (see, e.g. Gratton, Sneden, & Carretta (2004); Carretta et al (2009); Milone et al (2012); Piatti (2020)), open clusters still retain the mantle of single-generation parametric homogene-ity, apart from abundance variations due to the internal evolution of specific elements like Li or CNO. In particular, in the case of M67, diffusion and rotational mixing have arisen as a potential sources of significant multi-elemental variations with evolutionary phase (Souto et al 2019;Boesgaard, Lum, & Deliyannis 2020).…”

Section: Introductionmentioning

confidence: 99%

A uvbyCaHbeta CCD Analysis of the Open Cluster Standard, M67,and its Relation to NGC 752

Twarog¹,

Anthony-Twarog²,

Deliyannis³

2023

Preprint

View full text Add to dashboard Cite

Precision CCD uvbyCaHβ photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005-0.020 mag level to V ∼ 17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial-velocity information. From single-star members, offsets in the sense (M67 -NGC 752) are δE(b − y) = -0.005 ± 0.001 (sem) mag from 327 F/G dwarfs and δ[Fe/H] = 0.062 ± 0.006 (sem) dex from the combined m 1 and hk indices of 249 F dwarfs, leading to E(b − y) = 0.021 ± 0.004 (sem), and [Fe/H] M 67 = +0.030 ± 0.016 (sem) assuming [Fe/H] Hyades = +0.12. With probable binaries eliminated using c 1 , (b − y) indices, 83 members with (π/σ π ) > 50 generate (m − M ) 0 = 8.220 ± 0.005 (sem) for NGC 752 and an isochronal age of 1.45 ± 0.05 Gyr. Using the same parallax restriction for 312 stars, M67 has (m − M ) = 9.77 ± 0.02 (sem), leading to an age tied solely to the luminosity of the subgiant branch of 3.70 ± 0.03 Gyr. The turnoff color spread implies ± 0.1 Gyr, but the turnoff morphology defines a younger age/higher mass for the stars, consistent with recent binary analysis and broad-band photometry indicating possible missing physics in the isochrones. Anomalous stars positioned blueward of the turnoff are discussed.

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Different sodium enhancements among multiple populations of Milky Way globular clusters

Cited by 5 publications

References 38 publications

The surroundings of the Milky Way globular cluster NGC 6809

The surroundings of the Milky Way globular cluster NGC 6809

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

A uvbyCaHbeta CCD Analysis of the Open Cluster Standard, M67,and its Relation to NGC 752

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