Disc galaxies with multiple triaxial structures. II. JHK surface photometry and numerical simulations^*

¹ Observatoire de Genève, CH-1290 Sauverny, Switzerland
² Observatoire de Marseille, F-13248 Marseille Cedex 4, France
³ Steward Observatory, University of Arizona, Tucson AZ 85721, U.S.A.

Corresponding author: Send offprint request to: D. Friedli, e-mail: daniel.Friedli@obs.unige.ch

Received: 16 October 1995
Accepted: 2 February 1996

Abstract

We present detailed JHK surface photometry with ellipse fits of 13 galaxies selected from previous optical observations as likely candidates for having a secondary bar or a triaxial bulge within the primary bar. We have found 7 double-barred galaxies, 3 double-barred galaxies with an additional intermediate structure with twisted isophotes, and 3 galaxies with a bar and central twisted isophotes. A global analysis of the structural parameter characteristics in the I- and K-bands is presented. Various numerical models of galaxies with bars within bars are also analysed using the ellipse fitting technique and compared to the observations. A thorough review of the possible hypotheses able to explain this phenomenon is given with emphasis on the most likely ones.