High-resolution near-infrared spectra of NGC 6624 and 6569

Abstract

We present the first abundance analysis based on high-resolution infrared (IR) echelle spectra of NGC 6569 and 6624, two moderately reddened globular clusters located in the outer bulge of the Galaxy. We find [Fe/H]=-0.79 ± 0.02 and -0.69 ± 0.02 dex for NGC 6569 and 6624, respectively, and an average α-element enhancement of ≈+0.43 ± 0.02 and +0.39 ± 0.02 dex, consistent with previous measurements on other metal-rich bulge clusters. We measure accurate radial velocities of 〈vr〉=-47 ± 4 and +51 ± 3kms-1 and velocity dispersions of ≈8 and 6kms-1 for NGC 6569 and 6624, respectively. Finally, we find very low 12C/13C isotopic ratio (≤7 in NGC 6624 and ≈5 in NGC 6569), confirming the presence of extramixing mechanisms during the red giant branch evolution phase. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.