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
Origlia L., Valenti E., Rich R. M., Ferraro F. R. (2005). Near-infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity bulge globular clusters. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 363, 897-904 [10.1111/j.1365-2966.2005.09490.x].
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, respectivelyI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
