Volume 491, Number 3, December I 2008
|Page(s)||781 - 787|
|Section||Galactic structure, stellar clusters, and populations|
|Published online||15 October 2008|
The long Galactic bar as seen by UKIDSS Galactic plane survey
Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
2 GTC Project Office, 38205 La Laguna, Tenerife, Spain e-mail: firstname.lastname@example.org
3 Departamento de Astrofísica, Universidad de La Laguna, 8205 La Laguna, Tenerife, Spain
Accepted: 13 September 2008
Context. Over the past decade there have been a series of results supporting the hypothesis of the existence of a long thin bar in the Milky Way with a half-length of 4.5 kpc and a position angle of around 45°. This is apparently a very different structure from the triaxial bulge of the Galaxy, which is thicker and shorter and dominates the star counts at .
Aims. In this paper, we analyse the stellar distribution in the inner Galaxy to see if there is clear evidence for two triaxial or bar-like structures in the Milky Way.
Methods. By using the red-clump population as a tracer of Galactic structure, we determine the apparent morphology of the inner Galaxy. Deeper and higher spatial-resolution near infrared photometry from the UKIDSS Galactic plane survey allows us to use in-plane data even at the innermost Galactic longitudes, a region where the source confusion is a dominant effect that makes it impossible to use other databases, such as 2MASS or TCS-CAIN.
Results. We show that results previously obtained with the red-clump giants are confirmed with the in-plane data from UKIDSS GPS. There are two different structures coexisting in the inner Galactic plane: one with a position angle of that can be traced from the Galactic centre up to ~10° (the Galactic bulge), and other with a larger position angle of , that ends around (the long Galactic bar).
Key words: Galaxy: general / Galaxy: stellar content / Galaxy: structure / infrared: stars
© ESO, 2008
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