Diffuse Stellar Light at 100 kpc Scales in M87

Abstract

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 $28 \hbox{mag arcsec}^{-2}$. 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.