Astronomy & Astrophysics

A&A 458, 79-88 (2006)
DOI: 10.1051/0004-6361:20065017

Globular cluster kinematics and X-ray emission in the early-type galaxy NGC 1399

S. Samurovic^{1, 2, 3} and I. J. Danziger²

¹ Dipartimento di Astronomia, Università di Trieste, via Tiepolo 11, 34131 Trieste, Italy
e-mail: srdjan@ts.astro.it
² INAF, Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
e-mail: danziger@ts.astro.it
³ Astronomical Observatory, Volgina 7, 11160 Belgrade, Serbia and Montenegro

(Received 13 February 2006 / Accepted 7 July 2006 )

Abstract
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 $R_{\rm e}$ there is evidence that dark matter exists beyond ${\sim} 3\,R_{\rm e}$ .

Key words: Galaxy: kinematics and dynamics -- galaxies: elliptical and lenticular, cD -- galaxies: structure -- dark matter -- galaxies: individual: NGC 1399 -- Galaxy: star clusters