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arXiv · 0711.1779

NIR spectroscopy of the most massive open cluster in the Galaxy: Westerlund 1

S. Mengel·L. E. Tacconi-Garman
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Abstract

Using ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars in the central 2'x2' of the cluster Westerlund 1 (Wd 1) with a resolution of R~9000 at a central wavelength of 2.30 micron. This allowed us to determine radial velocities of ten post-main-sequence stars, and from these values a velocity dispersion. Assuming virial equilibrium, the dispersion of sigma=8.4 km/s leads to a total dynamical cluster mass of 1.25x10^5 solar masses, comparable to the photometric mass of the cluster. There is no extra-virial motion which would have to be interpreted as a signature of cluster expansion or dissolution.

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S. Mengel, L. E. Tacconi-Garman. 2007-11-12. NIR spectroscopy of the most massive open cluster in the Galaxy: Westerlund 1. https://doi.org/10.1017/s1743921308015433

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