Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-11-12
Astronomy and Astrophysics
Astrophysics
To appear in the proceedings of IAU 246: "Dynamical Evolution of Dense Stellar Systems" (E. Vesperini, M. Giersz, A. Sills, ed
Scientific paper
10.1017/S1743921308015433
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.
Mengel Sabine
Tacconi-Garman Lowell Evan
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