2013/08/02 by Christopher Wegg, Ortwin Gerhard · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Bulge #Extinction (optical mineralogy) #Galactic Center #Galactic plane #Galaxy #Globular cluster #Line-of-sight #Milky Way #Physics #Position angle #Red clump #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stt1376
14 pages, 19 figures, accepted by MNRAS
arxiv created 2013/08/02 · openalex publication_date 2013/09/09 · arxiv updated 2015/06/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The inner Milky Way is dominated by a boxy, triaxial bulge which is believed to have formed through disc instability processes. Despite its proximity, its large-scale properties are still not very well known, due to our position in the obscuring Galactic disc. Here, we make a measurement of the three-dimensional density distribution of the Galactic bulge using red clump giants identified in DR1 of the Vista Variables in the Via Lactea survey. Our density map covers the inner (2.2 × 1.4 × 1.1) kpc of the bulge/bar. Line-of-sight density distributions are estimated by deconvolving extinction- and completeness-corrected Ks-band magnitude distributions. In constructing our measurement, we assume that the three-dimensional bulge is eightfold mirror triaxially symmetric. In doing so, we measure the angle of the bar–bulge to the line of sight to be (27 ± 2)°, where the dominant error is systematic arising from the details of the deconvolution process. The resulting density distribution shows a highly elongated bar with projected axis ratios ≈(1 : 2.1) for isophotes reaching ∼2 kpc along the major axis. Along the bar axes the density falls off roughly exponentially, with axis ratios (10 : 6.3 : 2.6) and exponential scalelengths (0.70 : 0.44 : 0.18) kpc. From about 400 pc above the Galactic plane, the bulge density distribution displays a prominent X-structure. Overall, the density distribution of the Galactic bulge is characteristic for a strongly boxy/peanut-shaped bulge within a barred galaxy.