The long Galactic bar as seen by UKIDSS Galactic plane survey

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 degrees. 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 vertical bar l vertical bar < 10 degrees. 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 23 degrees.60 +/- 2 degrees.19 that can be traced from the Galactic centre up to similar to 10 degrees (the Galactic bulge), and other with a larger position angle of 42 degrees.44 +/- 2 degrees.14, that ends around l = 28 degrees (the long Galactic bar).