Using the `son of ISAAC' (Infrared Spectrometer And Array Camera) imager at the European Southern Observatory New Technology Telescope and the near-infrared spectrographs on Keck II, we have obtained J, K images and echelle spectra covering the range 1.5-1.8mum for the intermediate metallicity bulge globular clusters NGC 6539 and UKS 1. We find [Fe/H]=-0.76 and -0.78, respectively, and an average alpha-enhancement of ~+0.44 and ~+0.31 dex, consistent with previous measurements of metal-rich bulge clusters, and favouring the scenario of rapid chemical enrichment. We also measure very low 12C/13C ~ 4.5 +/- 1 isotopic ratios in both clusters, suggesting that extra-mixing mechanisms due to cool bottom processing are at work during evolution along the red giant branch. Finally, we measure accurate radial velocities of =+31 +/- 4 and =+57 +/- 6 km s-1 and velocity dispersions of ~8 and ~11 km s-1 for NGC 6539 and UKS 1, respectively

Near-infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity bulge globular clusters

VALENTI, ELENA;FERRARO, FRANCESCO ROSARIO
2005

Abstract

Using the `son of ISAAC' (Infrared Spectrometer And Array Camera) imager at the European Southern Observatory New Technology Telescope and the near-infrared spectrographs on Keck II, we have obtained J, K images and echelle spectra covering the range 1.5-1.8mum for the intermediate metallicity bulge globular clusters NGC 6539 and UKS 1. We find [Fe/H]=-0.76 and -0.78, respectively, and an average alpha-enhancement of ~+0.44 and ~+0.31 dex, consistent with previous measurements of metal-rich bulge clusters, and favouring the scenario of rapid chemical enrichment. We also measure very low 12C/13C ~ 4.5 +/- 1 isotopic ratios in both clusters, suggesting that extra-mixing mechanisms due to cool bottom processing are at work during evolution along the red giant branch. Finally, we measure accurate radial velocities of =+31 +/- 4 and =+57 +/- 6 km s-1 and velocity dispersions of ~8 and ~11 km s-1 for NGC 6539 and UKS 1, respectively
2005
Origlia L.; Valenti E.; Rich R. M.; Ferraro F. R.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/23863
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