Galaxy destruction and diffuse light in clusters

Deep images of the Centaurus and Coma clusters reveal two spectacular arcs of diffuse light that stretch for over 100 kpc, yet are just a few kpc wide. At a surface brightness of m_b \sim 27-28th arcsec^-2, the Centaurus arc is the most striking example known of structure in the diffuse light component of a rich galaxy cluster. We use numerical simulations to show that this feature is most probably the tidal debris of a low surface brightness (LSB) disk galaxy that has been disrupted by galaxy harassment, primarily by the gravitational potential of NGC 4709. High surface brightness disk galaxies are more stable to tidal shocks and lose less stellar mass, therefore their tidal debris is significantly fainter. Spheroidal galaxies can also produce features in the diffuse light component, yet these are even more diffuse and not as narrow. Only a luminous LSB galaxy on a fairly radial orbit, whose disk is co-rotating with its orbital path past pericentre can provide an acceptable reproduction of the extent, width and brightness of the Centaurus arc. Features this prominent in clusters will be relatively rare, although at fainter surface brightness levels the diffuse light will reveal a wealth of structure. Deeper imaging surveys may be able to trace this feature for several times its presently observed extent and somewhere along the tidal debris, a fraction of the original stellar component of the disk will remain bound, but transformed into a faint spheroidal galaxy. It should be possible to confirm the galactic origin of the Centaurus arc by observing planetary nebulae along its length with redshifts close to that of NGC 4709