A&A 491, 781-787 (2008)
The long Galactic bar as seen by UKIDSS Galactic plane surveyA. Cabrera-Lavers1, 2, C. González-Fernández1, F. Garzón1, 3, P. L. Hammersley1, and M. López-Corredoira1
1 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
2 GTC Project Office, 38205 La Laguna, Tenerife, Spain
3 Departamento de Astrofísica, Universidad de La Laguna, 8205 La Laguna, Tenerife, Spain
Received 31 July 2008 / 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