paper

High resolution infrared spectra of bulge globular clusters: The extreme chemical abundances of Terzan 4 and Terzan 5

arXiv:astro-ph/0402193 · doi:10.1086/420704

Abstract

Using the NIRSPEC spectrograph at Keck II, we have obtained infrared echelle spectra covering the range for the highly reddened bulge globular clusters Terzan 4 and Terzan 5. The clusters are of interest because a blue horizontal branch in Terzan 4 is consistent with very low metallicity, while Terzan 5 has been proposed as possibly the most metal rich known Galactic globular cluster. We report the first detailed abundance analysis for stars in these clusters, and we find [Fe/H]=--1.60 and --0.21 dex for Terzan 4 and Terzan 5, respectively, confirming the presence of a large metallicity spread in the bulge as well as in the halo of the Galaxy. We find dex in Terzan 4 and dex in Terzan 5, consistent with what has been found for field stars in the bulge. The enhanced element abundances are also consistent with rapid chemical enrichment, most likely by type II SNe. Finally, we measure very low C/C ratios in all the giant stars, confirming that extra-mixing mechanisms due to {\it cool bottom processing} occur during evolution along the RGB.

In press in the Astronomical Journal, 20 pages, 7figures

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