The influence of interactions and minor mergers on the structure of galactic disks II. Results and interpretations

We present the second part of a detailed statistical study focussed on the effects of tidal interactions and minor mergers on the radial and vertical disk structure of spiral galaxies. In the first part we reported on the sam ple selection, observations, and applied disk models. In this paper the res ults are presented, based on disk parameters derived from a sample of 110 h ighly-inclined/edge-on galaxies. This sample consists of two subsamples of 49 interacting/merging and 61 non-interacting galaxies. Additionally, 41 of these galaxies were observed in the NIR. We find significant changes of th e disk structure in vertical direction, resulting in approximate to 15 time s larger scale heights and thus vertical velocity dispersions. The radial d isk structure, characterized by the cut-off radius and the scale length, sh ows no statistically significant changes. Thus, the ratio of radial to vert ical scale parameters, h/z(0), is approximate to 1.7 times smaller for the sample of interacting/merging galaxies. The total lack of typical flat disk ratios h/z(0) > 7 in the latter sample implies that vertical disk heating is most efficient for (extremely) thin disks. Statistically nearly all gala ctic disks in the sample (93%) possess non-isothermal vertical luminosity p rofiles like the sech (60%) and exp (33%) distribution, independent of the sample and passband investigated. This indicates that, in spite of tidal pe rturbations and disk thickening, the initial vertical distribution of disk stars is not destroyed by interactions or minor mergers.