2015/03/24 by M. Portail, Matthieu Portail, Christopher Wegg +3 · 93 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Bar (unit) #Bulge #Galaxy #Instability #Physics #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1093/mnrasl/slv048
published in Monthly Notices of the Royal Astronomical Society Letters 450(1), L66-L70 (Oxford University Press) · Accepted for publication in MNRAS Letters
arxiv created 2015/03/24 · openalex publication_date 2015/04/24 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract Recent observations have discovered the presence of a box/peanut or X-shape structure in the Galactic bulge. Such box/peanut structures are common in external disc galaxies, and are well known in N-body simulations where they form following the buckling instability of a bar. From studies of analytical potentials and N-body models, it has been claimed in the past that box/peanut bulges are supported by ‘bananas’, or x1v1 orbits. We present here a set of N-body models where instead the peanut bulge is mainly supported by brezel-like orbits, allowing strong peanuts to form with short extent relative to the bar length. This shows that stars in the X-shape do not necessarily stream along banana orbits which follow the arms of the X-shape. The brezel orbits are also found to be the main orbital component supporting the peanut shape in our recent made-to-measure dynamical models of the Galactic bulge. We also show that in these models the fraction of stellar orbits that contribute to the X-structure account for 40–45 per cent of the stellar mass.