Events at Physics |
NGC 205 and M32 are close satellites of the Andromeda (M31) galaxy, and are our nearest examples of a dwarf elliptical (dE) and compact elliptical (cE) galaxy, respectively. Photometric observations strongly suggest NGC 205 and M32 are currently undergoing tidal distortion from their interaction with M31. In NGC 205, this conclusion is strengthened by the observation of an unusual velocity profile. Despite earlier attempts, the orbit and progenitor properties of NGC 205 are not well known. We perform an optimized search for these unknowns by combining a genetic algorithm with restricted N-body simulations of the interaction. Using NGC 205's photometric and kinematic observations as constraints, we carry out an effective exploration of the parameter space that defines the orbit and internal structure/dynamics of the progenitor satellite. We find that orbits best matching the observables place NGC 205 on primarily radial orbits moving from the Northwest to the Southeast with the satellite currently residing just behind M31. NGC 205's velocity appears near escape velocity, signifying it is likely on its first M31 passage. We also present Keck DEIMOS observations of M32's stellar kinematics well beyond the r < 4 arc sec region probed in previous studies. The task is made challenging by the fact that M32 is projected against the bright/complicated inner regions of M31. Long-slit integrated light spectroscopy is used to measure the rotation curve of M32 out to a radius of about 1 arcmin. Beyond this radius, we present constraints based on multislit spectroscopy of resolved stars. The velocity distributions from the latter data set reveal a distinct M32 component. A by-product of our M32 study, is the characterization of the kinematics of the underlying M31 disk and inner spheroid.<br>