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The intrinsic equatorial ellipticity of bulges

Published online by Cambridge University Press:  01 July 2007

J. Méndez-Abreu ,
J. A. L. Aguerri ,
E. M. Corsini  and
E. Simonneau
J. Méndez-Abreu
Affiliation:
INAF-Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy email: [email protected]
J. A. L. Aguerri
Affiliation:
Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, E-38200 La Laguna, Spain email: [email protected]
E. M. Corsini
Affiliation:
Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 3, I-35122 Padova, Italy email: [email protected]
E. Simonneau
Affiliation:
Institute d'Astrophysique de Paris, C.N.R.S., 98 bis Boul. Arago, F-75014 Paris, France
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Abstract

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Traditionally, the study of the structural parameters of galaxies have been used to understand the bulge formation processes. However, one piece lost in this study is the three-dimensional shape of the bulges. In this work, 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 (GASP-2D) was used to perform the bidimensional bulge-disk decomposition of 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 bulges and misalignments between bulges and disks. About 80% of bulges in S0-Sb galaxies are not oblate but triaxial ellipsoids. Their mean axial ratio in the equatorial plane is 〈B/A〉=0.85. There is not significant dependence of their PDF on morphology, light concentration, and luminosity. The scenarios in which bulges assembled from mergers and/or grew over long times through disk secular evolution have to be tested against the derived PDF of bulge intrinsic ellipticities.

Keywords

galaxies: bulgesgalaxies: evolutiongalaxies: formationgalaxies: fundamental parametersgalaxies: photometrygalaxies: statisticsgalaxies: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S245: Formation and Evolution of Galaxy Bulges , July 2007 , pp. 139 - 140
Copyright
Copyright © International Astronomical Union 2008

References

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Méndez-Abreu, J., Aguerri, J. A. L., Corsini, E. M. & Simonneau, E. 2007, A&A (submitted)Google Scholar