Globular cluster kinematics and X-ray emission in the early-type galaxy NGC 1399
Dipartimento di Astronomia, Università di Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: email@example.com
2 INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: firstname.lastname@example.org
3 Astronomical Observatory, Volgina 7, 11160 Belgrade, Serbia and Montenegro
Accepted: 7 July 2006
Context.Of the various observational methods used to address the question of dark matter in early-type galaxies there is the possibility of spatial overlap in using kinematics of stars, clusters and X-ray halos.
Aims.To investigate methods for the determination of velocity distribution profiles and deviations from a Gaussian distribution using globular clusters in early-type galaxies, and the implications for dark matter.
Methods.The maximum likelihood method together with standard statistical procedures were used to calculate the velocity dispersion. A new “tracer mass estimator” was applied to obtain a mass estimate based on the globular clusters, which is then compared to the mass obtained using X-rays.
Results.In NGC 1399 the departures from a Gaussian distribution of the velocities at all radial distances are small. Our conclusion is that in spite of the observations that show that the velocity dispersion decreases between 4 and 10 Re there is evidence that dark matter exists beyond .
Key words: Galaxy: kinematics and dynamics / galaxies: elliptical and lenticular, cD / galaxies: structure / dark matter / galaxies: individual: NGC 1399 / Galaxy: star clusters
© ESO, 2006