Structural properties of disk galaxies: The intrinsic equatorial ellipticity of bulges

Details Structural properties of disk galaxies: The intrinsic equatorial ellipticity of bulges Structural properties of disk galaxies: The intrinsic equatorial ellipticity of bulges

2008-01-31

arxiv.org/abs/0802.0010v1

Astronomy and Astrophysics

Astrophysics

2 pages, 1 figure to appear in the proceedings of "Formation and Evolution of Galaxy Disks", Rome, October 2007, Eds. J. Funes

Scientific paper

The structural parameters of a magnitude-limited sample of 148 unbarred S0-Sb galaxies were derived to study the correlations between bulge and disk parameters as well as the probability distribution function (PDF) of the intrinsic equatorial ellipticity of bulges. A new algorithm (GASP2D) was used to perform the bidimensional bulge-disk decomposition of the J-band galaxy images extracted from the archive of the 2MASS survey. The PDF of intrinsic ellipticities was derived from the distribution of the observed ellipticities of the bulges and misalignments between the the bulges and disks. About 80% of the observed bulges are not oblate but triaxial ellipsoids. Their mean axial ratio in the equatorial plane is =0.85. There is not significant dependence of their PDF on morphology, light concentration or luminosity. This has to be explained by the different scenarios of bulge formation.