The nuclear dust disks of five nearby 3CR elliptical galaxies

Abstract

We present broad- and narrow-band WFPC2 images of the nuclear dust disks and rings of five low- z elliptical galaxies hosting 3C radio sources: NGC 383 (3C 31)/NGC 382, NGC 3862 (3C 264), NGC 4261 (3C 270), UGC 12064 (3C 449), and NGC 7720 (3C 465)/NGC 7720A. We detect resolved line emission in all the disks. In NGC 383, the line emission consists of a “bar” and spectacular filamentary arms to the north and south while in NGC 7720 and UGC 12064, it is extended along the major axis of the disks, suggesting a true physical association between the ionized material and the dust. The color maps clearly reveal that the disks of NGC 383, NGC 4261, NGC 7720, and possibly NGC 3862 are inclined. The disk of NGC 383 is the most disturbed and filamentary and appears to consist of an “inner” (∼0.5 kpc) and “outer” (∼2.5 kpc) disk. We suggest that the colors of the unresolved nuclei of NGC 383 and NGC 3862 may be partially accounted for by optical synchrotron emission (and may in fact dominate in NGC 3862) while in NGC 4261, the nuclear emission is completely dominated by line emission. The disk colors are generally redder than predicted by a simple “sandwich” model, suggesting that the disks cannot be simply treated as thin uniform sheets of dust. We have begun exploring radiative transfer models with varying dust composition, temperature, and distribution and preliminary results are very promising.