Color distributions in E-S0 galaxies II. Evidence for diffuse dust concentration in the disks of disky E-type galaxies

Reddening of the major axis compared to the minor axis on a given isophote, and asymmetry of the run of surface brightness and colour along the minor axis, are possible signatures of dust concentrated in the disk of an inclined two components galaxy, the first being somewhat ambiguous. From CFHT observations, these phenomena are shown to occur in nearly all disky ellipticals of sufficient flattening. They may also occur in the inner “decoupled” disks, appearing in some ellipticals both boxy and disky. HST frames in Lauer et al. (1995) for a few objects confirm the present findings. Future modelling of diffuse dust in E classified galaxies should take into account this property of its distribution.