Properties of tidally-triggered vertical disk perturbations

We present a detailed analysis of the properties of warps and tidally-trigg ered perturbations perpendicular to the plane of 47 interacting/merging edg e-on spiral galaxies. The derived parameters are compared with those obtain ed for a sample of 61 non-interacting edge-on spirals. The entire optical ( R-band) sample used for this study was presented in two previous papers. We find that the scale height of disks in the interacting/merging sample is c haracterized by perturbations on both large (similar or equal to disk cut-o ff radius) and short (similar or equal to z(0)) scales, with amplitudes of the order of 280 pc and 130 pc on average, respectively. The size of these large (short) -scale instabilities corresponds to 14% (6%) of the mean disk scale height. This is a factor of 2 (1.5) larger than the value found for non-interacting galaxies. A hallmark of nearly all tidally distorted disks is a scale height that increases systematically with radial distance. The f requent occurrence and the significantly larger size of these gradients ind icate that disk asymmetries on large scales are a common and persistent phe nomenon, while local disturbances and bending instabilities decline on shor ter timescales. Nearly all (93%) of the interacting/merging and 45% of the non-interacting galaxies studied are noticeably warped. Warps of interactin g/merging galaxies are approximate to2.5 times larger on average than those observed in the non-interacting sample, with sizes of the order of 340 pc and 140 pc, respectively. This indicates that tidal distortions do consider ably contribute to the formation and size of warps. However, they cannot en tirely explain the frequent occurrence of warped disks.