2013/09/23 by I. Dékány, D. Minniti, M. Catelan +4
Physics and Astronomy · Social Sciences · #Astronomy and Astrophysical Research #Bimodality #Bulge #Educational Leadership and Practices #Galactic Center #Milky Way #Photometry (optics) #RR Lyrae variable #Red clump #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1088/2041-8205/776/2/l19
Accepted for publication in The Astrophysical Journal Letters, copyright AAS 2013
arxiv created 2013/09/23 · openalex publication_date 2013/10/03 · arxiv updated 2015/01/21 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have combined optical and near-infrared data of known RR Lyrae (RRL) stars in the bulge in order to study the spatial distribution of its metal-poor component by measuring precise reddening values and distances of 7663 fundamental-mode RRL stars with high-quality photometry. We obtain a distance to the Galactic center of R 0 = 8.33 ± 0.05 ± 0.14 kpc. We find that the spatial distribution of the RRL stars differs from the structures traced by the predominantly metal-rich red clump (RC) stars. Unlike the RC stars, the RRL stars do not trace a strong bar, but have a more spheroidal, centrally concentrated distribution, showing only a slight elongation in its very center. We find a hint of bimodality in the density distribution at high southern latitudes ( b < −5°), which needs to be confirmed by extending the areal coverage of the current census. The different spatial distributions of the metal-rich and metal-poor stellar populations suggest that the Milky Way has a composite bulge.