Conclusion

We believe that the observations reported in this paper, both long-slit spectroscopy and radio line-imaging, constitute the best observational indications up to now that the bar-buckling instability hypothesis to form boxy/peanut-shaped bulge spiral galaxies is correct. The previous evidence came mainly from imaging (photometric comparison with various models), but the strong line-splitting seen in the emission line spectra reported here agrees well with the kinematical predictions of Kuijken & Merrifield (1995) and Merrifield (1996) barred galaxy models. On the other hand, as much as our data support the bar-buckling scenario, they also raise many questions about the details of the models and their predictions. Our observations stress the need for more realistic models to be made, and for a better exploration of parameter-space, so that the models may be used to diagnose precisely the structure and dynamics of the galaxies. The question of how to discriminate between a bar and rings in an axisymmetric galaxy should also be addressed in more details.

Of course, the long-slit spectroscopy and HI line-imaging observations do not allow us to get a complete picture of the boxy/peanut bulge phenomenom, even when more sample galaxies are analysed. They mostly (but certainly not only) test the validity of the bar-boxy/peanut bulge association. Only when the optical and near-infrared imaging data are combined with the optical long-slit spectroscopy and the HI line-imaging data will we get, hopefully, a more complete picture of the structure, dynamics, and formation mechanism of this class of object.

© Copyright Astronomical Society of Australia 1997