2006AJ....132.2424W

NGC 5128, a giant elliptical galaxy only ∼4 Mpc away, is the dominant member of a galaxy group of over 80 probable members. The Centaurus group provides an excellent sample for a kinematic comparison between the halo of NGC 5128 and its surrounding satellite galaxies. A new study, presented here, shows no kinematic difference in rotation amplitude, rotation axis, or velocity dispersion between the halo of NGC 5128, determined from over ∼340 of its globular clusters, and those of the Centaurus group as a whole. These results suggest NGC 5128 could be behaving in part as the inner component to the galaxy group, and could have begun as a large initial seed galaxy, gradually built up by minor mergers and satellite accretions, consistent with simple cold dark matter models. The masses and mass-to-light ratios in the B band, corrected for projection effects, are determined to be (1.3±0.5)x10¹² M_☉ and 52±22 M_☉/L_☉ for NGC 5128 out to a galactocentric radius of 45 kpc and (9.2±3.0)x10¹² M_☉ and 153±50 M_☉/L_☉ for the Centaurus group, consistent with previous studies.