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American Astronomical Society, Astrophysical Journal, 2(791), p. 101, 2014

DOI: 10.1088/0004-637x/791/2/101

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Chemical and kinematical properties of Galactic bulge stars surrounding the stellar system Terzan 5

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

As part of a study aimed at determining the kinematical and chemical properties of Terzan 5, we present the first characterization of the bulge stars surrounding this puzzling stellar system. We observed 615 targets located well beyond the tidal radius of Terzan 5 and we found that their radial velocity distribution is well described by a Gaussian function peaked at =+21.0±4.6 km/s and with dispersion sigma_v=113.0±2.7 km/s. This is the one of the few high-precision spectroscopic survey of radial velocities for a large sample of bulge stars in such a low and positive latitude environment (b=+1.7{\deg}). We found no evidence for the peak at ∼+200 km/s found in Nidever et al. 2012. The strong contamination of many observed spectra by TiO bands prevented us from deriving the iron abundance for the entire spectroscopic sample, introducing a selection bias. The metallicity distribution was finally derived for a sub-sample of 112 stars in a magnitude range where the effect of the selection bias is negligible. The distribution is quite broad and roughly peaked at solar metallicity ([Fe/H]≃+0.05 dex) with a similar number of stars in the super-solar and in the sub-solar ranges. The population number ratios in different metallicity ranges agree well with those observed in other low-latitude bulge fields suggesting (i) the possible presence of a plateau for |b|