http://arxiv.org/abs/1911.04716
Studies of the red clump giant population in the inner Milky Way suggest the Galactic bulge/bar has a boxy/peanut/X-shaped structure as predicted by its formation via a disc buckling instability. We used a new non-parametric method of estimating the Galactic bulge morphology that is based on maximum entropy methods. With our maximum entropy deconvolution method we extracted the three-dimensional distribution of the red giant stars in the bulge from deep photometric catalogues of the VISTA Variables in the Via Lactea (VVV) survey. Our high-resolution reconstruction confirms the well known boxy/peanut/X-shaped structure of the bulge and also shows spurs which extend to around three kpc in front of and behind the bulge. One of those spurs is above the major axis of the bulge and the other is below the major axis. This is a key diagnostic of a post-buckling phase of the bulge. Additionally, at distances over 500 pc above or below the Galactic plane we find that the X-arms are on the same side of the bulge major axis as their corresponding spurs. Closer to the Galactic plane, the X-arms are on opposite sides of the major axis of the bulge. This implies a twisting in the X-shape of the bulge.
D. Paterson, B. Coleman and C. Gordon
Wed, 13 Nov 19
15/73
Comments: 10 pages, 7 figures