THE NATURE OF BOXY PEANUT SPIRAL GALAXIES - OVERVIEW AND NEW RESULTS/

The formation mechanism of boxy/peanut-shaped bulges in spiral galaxie s has been a problem for many years. We briefly review here the possib le formation scenarios for boxy/peanut bulges, concentrating on both t he bar-buckling and accretion hypotheses, and then describe an observa tional program aimed at testing those various theories and studying th e vertical structure of edge-on bars. Our program includes optical lon g-slit spectroscopy, HI line-imaging, near-infrared imaging, and multi -band optical imaging. New spectroscopic results (both optical and HI) are presented on seven galaxies, including five boxy/peanut-bulge spi rals. Based on Kuijken & Merrifield's (1995) idea for detecting edge-o n bars, we argue that these observations constitute a strong case in f avour of the bar-buckling mechanism for the formation of boxy/peanut-s haped bulges, but they also raise many questions and prompt for more d etailed modelling to be made. The implications of the observations con cerning the determination of rotation curves and of the physical condi tions in bulges are also discussed.