Open AccessNear‐infrared photometry and spectroscopy of NGC 6539 and UKS 1: two intermediate metallicity bulge globular clusters ★
Author(s) -
Origlia L.,
Valenti E.,
Rich R. M.,
Ferraro F. R.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.09490.x
Subject(s) - physics , globular cluster , bulge , astrophysics , metallicity , photometry (optics) , spectroscopy , astronomy , very large telescope , spectrometer , red giant branch , near infrared spectroscopy , stars , optics
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 1.5–1.8 μm 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 α‐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 12 C/ 13 C ≈ 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 〈 v r 〉=+31 ± 4 and 〈 v r 〉=+57 ± 6 km s −1 and velocity dispersions of ≈8 and ≈11 km s −1 for NGC 6539 and UKS 1, respectively,