The ACS survey of Galactic globular clusters – XIV. Bayesian single-population analysis of 69 globular clusters

Wagner-Kaiser, R.; Sarajedini, Ata; Hippel, Ted von; Stenning, David C.; Dyk, David A. van; Jeffery, Elizabeth; Robinson, Elliot; Stein, Nathan; Anderson, Jay; Jefferys, W. H.

doi:10.1093/mnras/stx544

Cited by 49 publications

(65 citation statements)

References 71 publications

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“…The results of SSP isochrone fitting are shown in Table 3 and Figures 9 and 10. The SSP age derivation of 13.7 ± 0.5 Gyr is in good agreement with Gratton et al (2003), that obtained 13.4 ± 1.1 Gyr, and with the Bayesian technique from Wagner-Kaiser et al (2017) that resulted in an age of 13.202 +0.174 −0.152 Gyr. The parallax from Gaia DR2 (Gaia Collaboration et al 2018b) for the NGC 6752, ω = 0.2610 ± 0.0011 mas, corrected by the zero point of −0.03 mas given by Lindegren et al (2018), gives a heliocentric distance of 3.85 ± 0.02 kpc.…”

Section: Application To the Halo Globular Cluster Ngc 6752supporting

confidence: 84%

“…Even though the uncertainties on the age derivation do not take into account the differences between the stellar evolutionary models, our uncertainty determinations are of the same order of magnitude as those by Monty et al (2018). Given that we did not propagate the uncertainties from the grid size of the parameter space, the uncertainties given here are the formal errors from MCMC algorithm and they are larger than the ones reported by Wagner-Kaiser et al (2017).…”

Section: Application To the Halo Globular Cluster Ngc 6752mentioning

confidence: 80%

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Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

Souza

Kerber

Barbuy

et al. 2020

ApJ

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The Bayesian isochrone fitting using the Markov chain Monte Carlo algorithm is applied, to derive the probability distribution of the parameters age, metallicity, reddening, and absolute distance modulus. We introduce the SIRIUS code by means of simulated color-magnitude diagrams, including the analysis of multiple stellar populations. The population tagging is applied from the red giant branch to the bottom of the main sequence. Through sanity checks using synthetic HST color-magnitude diagrams of globular clusters we verify the code reliability in the context of simple and multiple stellar populations. In such tests, the formal uncertainties in age or age difference, metallicity, reddening, and absolute distance modulus can reach 400 Myr, 0.03 dex, 0.01 mag, and 0.03 mag, respectively. We apply the method to analyse NGC 6752, using Dartmouth stellar evolutionary models. Assuming a single stellar population, we derive an age of 13.7 ± 0.5 Gyr and a distance of d = 4.11 ± 0.08 kpc, with the latter in agreement within 3σ with the inverse Gaia parallax. In the analysis of the multiple stellar populations, three populations are clearly identified. From the Chromosome Map and UV/Optical two-color diagrams inspection, we found a fraction of stars of 25 ± 5, 46 ± 7, and 29 ± 5 per cent, for the first, second, and third generations, respectively. These fractions are in good agreement with the literature. An age difference of 500 ± 410 Myr between the first and the third generation is found, with the uncertainty decreasing to 400 Myr when the helium enhancement is taken into account.

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Section: Application To the Halo Globular Cluster Ngc 6752supporting

confidence: 84%

Section: Application To the Halo Globular Cluster Ngc 6752mentioning

confidence: 80%

Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

Souza

Kerber

Barbuy

et al. 2020

ApJ

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“…The formal GCs ages for 69 ACS clusters from Ref. [47] would look similar to the J18082002-5104378 line. systematic uncertainties were all under control, we plot the age for the formal uncertainty of J18082002-5104378, which is fully compatible with Planck18.…”

Section: Datamentioning

confidence: 75%

The local and distant Universe: stellar ages and H₀

Jiménez

Cimatti

Verde

et al. 2019

J. Cosmol. Astropart. Phys.

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The ages of the oldest stellar objects in our galaxy provide an independent test of the current cosmological model as they give a lower limit to the age of the Universe. Recent accurate parallaxes by the Gaia space mission, accurate measurements of the metallicity of stars, via individual elemental abundances, and advances in the modelling of stellar evolution, provide new, higher-precision age estimates of the oldest stellar populations in the galaxy: globular clusters and very-low-metallicity stars. The constraints on the age of the Universe, t U , so obtained are determined from the local Universe and at late time. It is well known that local and early-Universe determinations of another cosmological parameter closely related to the age of the Universe, the Hubble constant H 0 , show a 3σ tension. In the standard cosmological model, ΛCDM, t U and H 0 are related by the matter density parameter Ω m,0 . We propose to combine local t U constraints with late-time Ω m,0 estimates in a ΛCDM framework, to obtain a low-redshift H 0 determination that does not rely on early Universe physics. A proof-of-principle of this approach with current data gives H 0 = 71 ± 2.8 (H 0 = 69.3 ± 2.7) km s −1 Mpc −1 from globular clusters (very-low-metallicity stars) with excellent prospects for improved constraints in the near future.

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“…NGC 1851 is a moderately metal-poor globular cluster located at an R GC of 17 kpc from the Galactic centre and ∼ 7 kpc below the disk plane (Harris 1996(Harris , 2010. Wagner-Kaiser et al (2017) find a cluster age of 11.5 Gyr. Some have argued for an evolutionary connection between NGC 1851 and several other clusters (NGC 1904, NGC 2808, and NGC 2298 on the basis of their spatial proximity (Bellazzini et al 2001), as we confirm by our abundances below.…”

Section: Ngc 1851mentioning

confidence: 81%

Non-LTE chemical abundances in Galactic open and globular clusters

Kovalev

Bergemann

Ting

et al. 2019

A&A

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Aims. We study the effects of non-local thermodynamic equilibrium (NLTE) on the determination of stellar parameters and abundances of Fe, Mg, and Ti from the medium-resolution spectra of FGK stars. Methods. We extend the Payne fitting approach to draw on NLTE and LTE spectral models. These are used to analyse the spectra of the Gaia-ESO benchmark stars and the spectra of 742 stars in 13 open and globular clusters in the Milky Way: NGC 3532, NGC 5927, NGC 2243, NGC 104, NGC 1851, NGC 2808, NGC 362, M2, MGC 6752, NGC 1904 Results. Our approach accurately recovers effective temperatures, surface gravities, and abundances of the benchmark stars and clusters members. The differences between NLTE and LTE are significant in the metal-poor regime, [Fe/H] −1. The NLTE [Fe/H] values are systematically higher, whereas the average NLTE [Mg/Fe] abundance ratios are ∼ 0.15 dex lower, compared to LTE. Our LTE measurements of metallicities and abundances of stars in Galactic clusters are in a good agreement with the literature. Yet, for most clusters, our study yields the first estimates of NLTE abundances of Fe, Mg and Ti. Conclusions. All clusters investigated in this work are homogeneous in Fe and Ti, with the intra-cluster abundance variations of less then 0.04 dex. NGC 2808, NGC 4833, M2 and M 15 show significant dispersions in [Mg/Fe]. Contrary to common assumptions, the NLTE analysis changes the mean abundance ratios in the clusters, but it does not influence the intra-cluster abundance dispersions.

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The ACS survey of Galactic globular clusters – XIV. Bayesian single-population analysis of 69 globular clusters

Cited by 49 publications

References 71 publications

Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

The local and distant Universe: stellar ages and H₀

Non-LTE chemical abundances in Galactic open and globular clusters

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The ACS survey of Galactic globular clusters – XIV. Bayesian single-population analysis of 69 globular clusters

Cited by 49 publications

References 71 publications

Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

Self-consistent Analysis of Stellar Clusters: An Application to HST Data of the Halo Globular Cluster NGC 6752

The local and distant Universe: stellar ages and H0

Non-LTE chemical abundances in Galactic open and globular clusters

Contact Info

Product

Resources

About

The local and distant Universe: stellar ages and H₀