Bibcode
Mendez-Abreu, J.; Aguerri, J. A. L.; Corsini, E. M.; Simonneau, E.
Bibliographical reference
Galaxy Evolution Across the Hubble Time, Edited by F. Combes and J. Palous, Proceedings of the International Astronomical Union 2, IAU Symposium #235, held 14-17 August, 2006 in Prague, Czech Republic. Cambridge: Cambridge University Press, 2007., pp.123-123
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2007
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Description
Evidences suggesting that bulges of non-barred disk galaxies could be
triaxial structures come from different aspects. From the photometry,
the twist of the inner isophotes and the misaligment between the disk
and the bulge major axis position angle are not possible under the
hypothesis of symmetry for both components. From the kinematics,
rotation curves with velocities higher than permitted by circular
motions or velocity gradients along the galaxy minor axis can be
understood as signs of triaxiality. If triaxiality is a common feature
in bulges, it could have important implications on bulge formation and
evolution. Asymmetries in the potential could provide a method of
transporting gas into the galaxy center, and therefore must be consider
when accounting for fuelling of central starbursts, for the formation of
inner rings or for the formation and destruction of bars due to the
build up of gas in the galactic center. Following the previous
statistical works on bulges triaxiality (Zaritsky & Lo,1986; Bertola
et al., 1991), we have used a photometric approach to derive the
probability distribution function (PDF) of the intrinsic axis ratios of
bulges. In our work, we improve the previous ones in several aspects.
First, we use a more extensive (148 galaxies) and better defined sample
of non-barred disk galaxies. Second, we use a fully bidimensional code
to derive the photometric parameters of galaxies in the sample, using
images in the J-band taken from the 2MASS archive. And third, we
determine the PDF using a new method where the geometry of the system is
inverted analytically. As a preliminary result, we have found for our
sample of bulges that ˜ 44% are close to be oblate ellipsoids,
˜16 % are close to prolate ellipsoids, ˜5 % are close to be
spheres and the remaining ˜34 % are definitely triaxials
ellipsoids.