TY  - GEN
AV  - public
A1  - Schönebeck, Frederik
TI  - Velocity Dispersion Measurements of Milky Way Globular Clusters with VLT/X-shooter Spectroscopy
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/19581/
Y1  - 2015///
ID  - heidok19581
N2  - We have observed 29 globular clusters in the Magellanic Clouds and the Milky Way with VLT/X-shooter, a spectrograph with an exceptionally large spectral range from the ultraviolet to the near-infrared at moderately high resolution. The observations have been performed in drift-scan mode, where the telescope is slewed across the cluster during integration. Our comprehensive cascade of reduction steps allows for an uncertainty less than 10% in the absolute flux calibration and less than 0.02 angstrom in the wavelength calibration of the reduced spectra. For a subset of eleven clusters, for which accurate Hubble Space Telescope photometry is available, we construct detailed synthetic composite spectra based on their stellar populations, and subsequently use them as spectral templates to measure the velocity dispersion profile and radial velocity profile for each cluster. The obtained radial velocities indicate ordered rotation of some clusters. We use the central velocity dispersions to compute the dynamical masses and mass-to-light ratios for our sample. The sample median mass-to-light ratio is 1.7 M_sun / L_sun and fully consistent with a cluster mass that is entirely made up of stars and their remnants. In conjunction with our kinematic results follow-up numerical simulations will help to constrain the cluster mass profiles.
ER  -