Box- and peanut-shaped bulges: I. Statistics

Abstract

We present a classification for bulges of a complete sample of ~1350 edge-on disk galaxies derived from the RC3 (Third Reference Catalogue of Bright Galaxies, de Vaucouleurs et al. 1991). A visual classification of the bulges using the Digitized Sky Survey (DSS) in three types of b/p bulges or as an elliptical type is presented and supported by CCD images. NIR observations reveal that dust extinction does almost not influence the shape of bulges. There is no substantial difference between the shape of bulges in the optical and in the NIR. Our analysis reveals that 45% of all bulges are box- and peanut-shaped (b/p). The frequency of b/p bulges for all morphological types from S0 to Sd is > 40%. In particular, this is for the first time that such a large frequency of b/p bulges is reported for galaxies as late as Sd. The fraction of the observed b/p bulges is large enough to explain the b/p bulges by bars.