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We present the first dynamical study of the globular cluster system of NGC4636. This giant elliptical galaxy is claimed to be extremely dark matterdominated, according to X-ray observations. Using the VLT with FORS2/MXU, weobtained velocities for 174 globular clusters. The clusters have projectedgalactocentric distances in the range 4 to 70 kpc, the overwhelming majoritylie within 30 kpc. We find some indication for a rotation of the red(metal-rich) clusters about the minor axis. Out to a radius of 30 kpc, we finda roughly constant projected velocity dispersion for the blue clusters of ~200km/s. The red clusters exhibit a distinctly different behavior: at a radius ofabout 13 kpc, the velocity dispersion drops by ~50 km/s to about 170 km/s whichthen remains constant out to a radius of 30 kpc.  Using only the blue clusters as dynamical tracers, we perform Jeans-analysesfor different assumptions of the orbital anisotropy. Depending on theanisotropy and the adopted M/L-values, we find that the dark matter fractionwithin one effective radius can vary between 20% and 50% with most a probablerange between 20% and 30%. A main source of uncertainty is the ambiguity of thevelocity dispersion in the outermost bin.  Although the dark halo mass still cannot be strongly constrained, NGC 4636does not seem to be extremely dark matter dominated. The derived circularvelocities are also consistent with Modified Newtonian Dynamics.Comment: 19 pages, 18 figures. Accepted for publication in A&A. Appendix A  (velocity tables) will be published in the online version of the journa

Dynamics of the NGC 4636 globular cluster system