The tidal filament of NGC 4660
  NGC 4660, in the Virgo cluster, is a well-studied elliptical galaxy which has
a strong disk component (D/T about 0.2-0.3). The central regions including the
disk component have stellar populations with ages about 12-13 Gyr from SAURON
studies. However we report the discovery of a long narrow tidal filament
associated with the galaxy in deep co-added Schmidt plate images and deep CCD
frames, implying that the galaxy has undergone a tidal interaction and merger
within the last few Gyr. The relative narrowness of the filament implies a wet
merger with at least one spiral galaxy involved, but the current state of the
system has little evidence for this. However a 2-component photometric fit
using GALFIT shows much bluer B-V colours for the disk component than for the
elliptical component, which may represent a residual trace of enhanced star
formation in the disk caused by the interaction 1-2 Gyr ago. There are brighter
concentrations within the filament which resemble Tidal Dwarf Galaxies,
although they are at least 40 times fainter. These may represent faint, evolved
versions of these galaxies. A previously detected stripped satellite galaxy
south of the nucleus is seen in our residual image and may imply that the
filament is a tidal stream produced by perigalactic passages of this satellite.
