Large Stellar Disks in Small Elliptical Galaxies

Abstract

We present stellar kinematics along the principal axes of seven elliptical galaxies less luminous than MB = -19.5, which extend beyond the half-light radii for all systems in this photometrically selected sample. At large radii, the kinematics not only confirm that rotation and "diskiness" are important in faint elliptical galaxies, as was previously known, but show that rotation dominates: the stars at large galactocentric distances have (Vlσ)max ∼ 2, similar to the disks in bona fide S0 galaxies. A comparison with published simulations of dissipationless mergers is not straightforward. Yet, within Re, the observed galaxies seem to rotate somewhat faster than 3:1 merger remnants, arguing against major mergers as the dominant mechanism in the final shaping of low-luminosity elliptical galaxies and favoring instead the dissipative formation of a disk.