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We present the first dynamical study of the globular cluster system of NGC 4636. This giant elliptical galaxy is claimed to be extremely dark matter dominated, according to X-ray observations. Using the VLT with FORS2/MXU, we obtained velocities for 174 globular clusters. The clusters have projected galactocentric distances in the range 4 to 70 kpc, the overwhelming majority lie 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 find a roughly constant projected velocity dispersion for the blue clusters of ~200 km/s. The red clusters exhibit a distinctly different behavior: at a radius of about 13 kpc, the velocity dispersion drops by ~50 km/s to about 170 km/s which then remains constant out to a radius of 30 kpc. Using only the blue clusters as dynamical tracers, we perform Jeans-analyses for different assumptions of the orbital anisotropy. Depending on the anisotropy and the adopted M/L-values, we find that the dark matter fraction within one effective radius can vary between 20% and 50% with most a probable range between 20% and 30%. A main source of uncertainty is the ambiguity of the velocity dispersion in the outermost bin. Although the dark halo mass still cannot be strongly constrained, NGC 4636 does not seem to be extremely dark matter dominated. The derived circular velocities are also consistent with Modified Newtonian Dynamics.
We present a kinematic analysis of the globular cluster(GC) system in the giant elliptical galaxy (gE) NGC 4636 in the Virgo cluster. Using the photometric and spectroscopic database of 238 GCs, we have investigated the kinematics of the GC system. T
We present new radial velocities for 289 globular clusters around NGC 4636, the southernmost giant elliptical galaxy of the Virgo cluster. The data were obtained with FORS2/MXU at the Very Large Telescope. Together with data analysed in an earlier st
We present a spectroscopic study of the globular clusters (GCs) in the giant elliptical galaxy NGC 4636 in the Virgo cluster. We selected target GC candidates using the Washington photometry derived from the deep CCD images taken at the KPNO 4m. Then
This paper presents further results from our spectroscopic study of the globular cluster (GC) system of the group elliptical NGC 3923. From observations made with the GMOS instrument on the Gemini South telescope, an additional 50 GC and Ultra Compac
From observations with the GMOS multi-slit spectrograph on the Gemini North telescope, we have obtained spectra for 39 globular cluster candidates in the Virgo giant elliptical galaxy NGC 4649 (M60), of which 38 are confirmed globular clusters. The c