Infrared Echelle Spectroscopy of Palomar6 and M71

Abstract

We present high-resolution infrared echelle spectroscopy for the globular clusters Palomar 6 and M71. Our mean heliocentric radial velocity of Palomar 6 is +180.6 +/- 3.2 km sec/s and is 20 km/s lower than that found by Minniti in 1995. Contrary to the previous metallicity estimates using low-resolution spectroscopy, our results show that Palomar~6 has an intermediate metallicity with [Fe/H] = -1.0 +/- 0.1 and is slightly more metal-poor than M71. Reasonable changes in the surface temperature or the microturbulent velocity of the model atmospheres do not affect [Fe/H] at more than +/- 0.2 dex. In spite of its high metallicity, based on the spectrum of a single cluster member the [Si/Fe] and [Ti/Fe] ratios of Palomar~6 appear to be enhanced by 0.4 dex and 0.5 dex, respectively, suggesting that the Galactic inner halo may have experienced a very rapid chemical enrichment history.