Astron. Astrophys. Suppl. Ser. 145, 405-414

Box- and peanut-shaped bulges

I. Statistics

R. Lütticke - R.-J. Dettmar - M. Pohlen

Astronomisches Institut, Ruhr-Universität Bochum, D-44780 Bochum, Germany
e-mail: luett@astro.ruhr-uni-bochum.de

Received May 11; accepted June 13, 2000

Abstract:

We present a classification for bulges of a complete sample of $\sim$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.

Key words: galaxies: evolution -- galaxies: spiral -- galaxies: statistics -- galaxies: structure