EDP Sciences
Free access
Volume 491, Number 3, December I 2008
Page(s) 781 - 787
Section Galactic structure, stellar clusters, and populations
DOI http://dx.doi.org/10.1051/0004-6361:200810720
Published online 15 October 2008

A&A 491, 781-787 (2008)
DOI: 10.1051/0004-6361:200810720

The long Galactic bar as seen by UKIDSS Galactic plane survey

A. 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
    e-mail: antonio.cabrera@gtc.iac.es
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 $\vert l\vert<10^\circ$.
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 $23\fdg 60 \pm 2\fdg 19$ that can be traced from the Galactic centre up to ~10° (the Galactic bulge), and other with a larger position angle of $42 \fdg 44 \pm 2\fdg 14$, that ends around $l=28^\circ$ (the long Galactic bar).

Key words: Galaxy: general -- Galaxy: stellar content -- Galaxy: structure -- infrared: stars

© ESO 2008