Precise reddening and metallicity of NGC6752 from FLAMES spectra

Abstract

(abridged) Accurate reddenings for Globular Clusters could be obtained by comparing the colour-temperature obtained using temperatures from reddening-free indicator (Halpha), with that given by standard colour-temperature calibrations. From a single 1300 seconds exposure with FLAMES at VLT2 we obtained spectra centred on Halpha (R=6000, 5<S/N<50) for 120 stars near the turn-off of NGC6752. This set of spectra was used to derive effective temperatures from fittings of Halpha profiles with typical errors of about +/- 200 K and reddening estimates with individual errors of 0.05 mag. Averaging all individual reddenings, a high precision reddening estimate has been obtained for the cluster: E(B-V)=0.046 +/- 0.005. The same exposure provided UVES spectra of seven stars near the red giant branch bump (R=40000, 20<S/N<40) that provided Fe abundances with internal errors of 0.026 dex, and with average metallicity [Fe/H]= -1.48 +/- 0.01 +/- 0.06 dex (random + systematic). Abundances were obtained for several other elements, allowing e.g. an accurate estimate of the ratio between the alpha-elements and Fe ([alpha/Fe]=+0.27 +/- 0.01). The O-Na anticorrelation is evident from our UVES data, in agreement with past results. This analysis shows the power of FLAMES for analysis of globular clusters: the accurate reddenings and metal abundances obtained by a procedure like that described here, combined with distance determinations from cluster dynamics or main sequence fitting, and high quality colour-magnitude diagrams, could allow derivation of ages with errors below 1 Gyr for individual globular clusters.

arXiv commentaccepted for publication on A&A

References in corpus (19)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters
• Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant
• The New Galaxy: Signatures of its Formation
• The second US Naval Observatory CCD Astrograph Catalog (UCAC2)
• The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
• Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB
• Distances, ages, and epoch of formation of globular clusters
• Distances and ages of NGC 6397, NGC 6752 and 47 Tuc
• Ages of Globular Clusters from Hipparcos Parallaxes of Local Subdwarfs
• Galactic Globular Cluster Relative Ages
• Abundances of C, N, O in slightly evolved stars in the globular clusters NGC 6397, NGC 6752 and 47 Tuc
• Galactic Globular Cluster Metallicity Scale from the Ca II Triplet. I. Catalog
• The initial Helium content of Galactic Globular Cluster stars from the R-parameter: comparison with the CMB constraint
• Mg isotopic ratios in giant stars of the globular cluster NGC 6752
• The Sgr dSph hosts a metal-rich population
• The Initial Helium Abundance of the Galactic Globular Cluster System
• The ubiquitous nature of the Horizontal Branch second U-jump: A link with the Blue Hook scenario?
• CCD Photometry of Faint Variable Stars in the Globular Cluster NGC 6752

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