SIMBAD references

Shells are interpreted as debris from interaction/acquisition episodes that occur in a galaxy. We present a study of the warm (T ~ 10⁴K) gas component in a sample of five shell galaxies belonging to the Malin & Carter compilation. Hα observations have been obtained at the ESO 3.6-m telescope equipped with a CIGALE scanning Fabry-Perot interferometer coupled with a new IPCS camera.

Most of our sample galaxies show disturbed/irregular gaseous velocity fields. The gas distribution in NGC 7070A and 7135 shows elongated, asymmetric structure relative to the stellar body. The continuum and line maps for ESO 2400100 show a double nucleus. The nuclei are slightly off-centre with respect to the barycentre of the pair, a deformation that cannot arise from projection effects and that suggests a strong on-going tidal interaction.

Kinematics of the stellar and gas component derived for NGC 1553 are similar, although the gas component shows evidence for non-circular motion. In most of our objects the gas and the stellar kinematics appear decoupled, but no rings of gas nor diffuse gas shells are detected. If shell galaxies form through an acquisition/merging event, the general hypothesis according to which the gas in Es is accreted from outside the galaxy is further supported by these data. We speculate concerning shell galaxy evolution using additional information coming from studies of line-strength indices.