Box- and peanut-shaped bulges

III. A new class of bulges: Thick Boxy Bulges

¹ Astronomical Institute, Ruhr-Universität Bochum, 44780 Bochum, Germany
² Department of Computer Science, Intelligent Information and Communication Systems, FernUniversität Hagen, Universitätsstr. 1, 58084 Hagen, Germany
³ Instituto de Astrofisica de Canarias, La Laguna, 38200 Tenerife, Spain

Corresponding author: R. Lütticke, rainer.luetticke@fernuni-hagen.de

Received: 3 December 2001
Accepted: 19 December 2003

Abstract

Inspecting all 1224 edge-on disk galaxies larger than 2′ in the RC3 on Digitized Sky Survey (DSS) images (Lütticke et al. [CITE]) we have found several galaxies with extraordinary bulges meeting two criteria: they are box shaped and large in respect to the diameters of their galaxies. These bulges are often disturbed, show frequently prominent irregularities and asymmetries, and some possess possible merger remnants or merging satellites. For these bulges we have introduced the term “Thick Boxy Bulges” (TBBs). About 2% of all disk galaxies (S0-Sd), respectively 4% of all galaxies with box- and peanut-shaped (b/p) bulges, belong to this class of galaxies. Using multicolour CCD and NIR data we have enlarged and followed up our sample of nearly 20 galaxies with a TBB. The disturbed morphology of a large fraction of these galaxies shows that many of the TBB galaxies are not dynamically settled. For the TBBs the extent of the box shape seems to be too large to result from a normal bar potential. Therefore we conclude that two classes of b/p bulges exist with different origins. While most (~96%) b/p bulges can be explained by bars alone (Lütticke et al. [CITE]), the extended boxy structures of TBBs result most likely from accreted material by infalling satellite companions (soft merging).