A statistical method is used to determine both the Sun's distance r0 from the Galactic Centre and the 3D structure of the old stellar population of the Galactic bulge. The space distribution of 16 221 high latitude type-RRab RR Lyrae stars from the optical OGLE survey located towards the bulge is explored. An estimate by using RR Lyraes leads to a mean r0 = 8.28 ± 0.14 kpc within the effective bulge radius of rbulge = 2-3 kpc. The distribution of RR Lyraes within rbulge has the shape of an ellipsoid slightly elongated almost towards the Sun with a major axis of its symmetry a and two minor axes b and c of about the same length. The axial ratio is a: b: c ~ 1: 0.7: 0.7. These age-old, metal-poor, and kinematically hot stars do not trace a strong bar-like structure in the direction of the bulge at distances >1 kpc from the Galactic Centre, as b/a ~ 1.
- Galaxy: bulge
- Galaxy: fundamental parameters
- Galaxy: kinematics and dynamics
- Galaxy: structure
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science