Detection of the old stellar component of the major Galactic bar

• DOI: 10.1046/j.1365-8711.2000.03858.x
• Publication Date: 2003-03-12T13:16:27Z
• Authors: P. L. Hammersley; F. Garzon; T. J. Mahoney; M. Lopez-Corredoira; M. A. P. Torres
• Keywords: Astrophysics (astro-ph); 0103 physical sciences; FOS: Physical sciences; Astrophysics; 01 natural sciences

We present near-IR colour--magnitude diagrams and star counts for a number of regions along the Galactic plane. It is shown that along the l=27 b=0 line of sight there is a feature at 5.7 +-0.7kpc with a density of stars at least a factor two and probably more than a factor five times that of the disc at the same position. This feature forms a distinct clump on an H vs. J-H diagram and is seen at all longitudes from the bulge to about l=28, but at no longitude greater than this. The distance to the feature at l=20 is about 0.5kpc further than at l=27 and by l=10 it has merged with, or has become, the bulge. Given that at l=27 and l=21 there is also a clustering of very young stars, the only component that can reasonably explain what is seen is a bar with half length of around 4kpc and a position angle of about 43+-7.<br/>5 pages, 5 figures accepted as a letter in MNRAS<br/>