8 Conclusions  

The large number of observational data presented in this work can be summarized as follow:
1) the peanut shape of the galaxy is clearly visible at optical and NIR wavelengths;
2) the color of the inner regions is rather uniform and similar to that of the disk component. A small color gradient toward the center is observed;
3) the stellar disk is thick and distorted, in particular toward the NW side;
4) the galaxy host a counter-rotating gas component which is tilted in the direction of the companion galaxy NGC 127. The mass of such component is approximately $\sim$$2.7\ 10^4 \ M_{\hbox{$\odot$}}$;
5) the gas has not the same distribution of the dust component which is largely confined in the region of interaction between NGC 128 and NGC 127. The mass of the dust component is estimated of $\sim$$6\ 10^6\ M_{\hbox{$\odot$}}$;
6) the gas does not seem to fuel a nuclear activity or a starburst of star formation;
7) the velocity field of the stellar component is approximately cylindrical. The velocity dispersion along the minor axis is rather constant and high. The RC of the gas component has the same slope of the stellar component;
8) the "figure-of-eight'' of the RC, signature characteristic for the presence of a bar, is not observed, either in the stellar and gaseous component.

The whole data-set presented in this paper does not clearly reveal or dismiss the presence of a bar in NGC 128 and seem to support the theoretical mixed scenario proposed by Mihos et al. (1995). Interactions and soft merging events probably triggered a disk instability which originate a strong buckling phenomenon. We can suspect that the interaction between NGC 128 and NGC 125 or the accretion of a small gas-rich satellite was responsible of such instability. The interaction with the spiral companion NGC 127 seems very recent since dust and gas have not the same spatial distribution in the galaxy.

Acknowledgements

We thank P. Rafanelli for the large field image of NGC 128 taken at Calar Alto, R. Assendorp for the valuable help in the IRAS data reductions, and B. Jarvis for the long slit RCs of NGC 128 perpendicular and parallel to the major axis. We are also very grateful to the observers of the Spectial Astrophysical Observarory, S.N. Dodonov, S.V. Drabek and V.V. Vlasiuk assisting us at the 6 m telescope, as well to J.L. Gach of Marseille Observatory for his help during observations and data reduction.