In a new survey of nearby galaxies from stacked photographic images, M87
shows a diffuse fan of stellar material which extends along the projected SE
(major) axis out to about 100 kpc at a limiting (B) surface brightness of 28mag arcsec−2. We suggest that disruption of a small spheroidal
galaxy within a larger potential is the most likely explanation for the diffuse
structure. Our simulations include a rigid primary potential with
characteristics similar to those derived for M87 and a populated intruder. The
orbit is required to pass close to the center of the potential to produce a fan
which nearly aligns with the major axis and has a large opening angle, as seen
in M87. The structure of the dark matter at large galactic radii is
investigated by representing M87 with different potentials. The morphology and
luminosity of the fan and the kinematics of debris in the center of the primary
potential are analyzed and compared with substructure in M87. The short
lifetimes (t_fan < 5 10^8 years) of the simulated diffuse fans indicate that
several accretion events could be hidden in galaxies.Comment: 24 pages, Latex (aaspp4.sty), with 15 figures. Accepted for
publication in Ap