Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2011-11-24
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
16 pages, 17 figures, Astronomy and Astrophysics in press, new submission after langage editing and minor corrections (includi
Scientific paper
We re-analyse photometric near-infrared data in order to investigate why it is so hard to get a consensus for the shape and density law of the bulge, as seen from the literature. To solve the problem we use the Besancon Galaxy Model to provide a scheme for parameter fitting of the structural characteristics of the bulge region. The fitting process allows the determination of the global shape of the bulge main structure. We explore various parameters and shape for the bulge/bar structure based on Ferrer's ellipsoids and fit the shape of the inner disc in the same process. The results show that the main structure is a quite standard triaxial boxy bar/bulge with an orientation of about 13 degree with respect to the Sun-centre direction. But the fit is greatly improved when we add a second structure, which is a longer and thicker ellipsoid. We emphasize that our first ellipsoid represent the main boxy bar of the Galaxy, and that the thick bulge could be either a classical bulge slightly flattened by the effect of the bar potential, or a inner thick disc counterpart. We show that the double clump seen at intermediate latitudes can be reproduced by adding a slight flare to the bar. In order to better characterize the populations, we further simulate several fields which have been surveyed in spectroscopy and for which metallicity distribution function (MDF) are available. The model is in good agreement with these MDF along the minor axis if we assume that the main bar has a mean solar metallicity and the second thicker population has a lower metallicity. It then creates naturally a vertical metallicity gradient by the mixing of the two poulations. (abridged)
Marshall Douglas J.
Reyle Céline
Robin Annie C.
Schultheis Mathias
No associations
LandOfFree
Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-157215