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Double X/Peanut structures in barred galaxies – insights from an N -body simulation

Journal Article · · Monthly Notices of the Royal Astronomical Society
 [1];  [2];  [3];  [4];  [5]
  1. GEPI, Observatoire de Paris, PSL Research University, Place Jules Janssen, F-92190 Meudon, France, LERMA, Observatoire de Paris, CNRS, PSL University, Sorbonne Universités, UPMC Univ. Paris 06, F-75014 Paris, France
  2. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany
  3. Leibniz Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany, Institute of Astronomy, Russian Academy of Sciences, 48 Pyatnitskya St, Moscow 119017, Russia, Max Planck Institute for Extraterrestrial Physics, D-85741 Garching, Germany
  4. GEPI, Observatoire de Paris, PSL Research University, Place Jules Janssen, F-92190 Meudon, France
  5. LERMA, Observatoire de Paris, CNRS, PSL University, Sorbonne Universités, UPMC Univ. Paris 06, F-75014 Paris, France, Collège de France, 12 Place Marcelin-Berthelot, F-75005 Paris, France
ABSTRACT

Boxy, peanut-, or X-shaped ‘bulges’ are observed in a large fraction of barred galaxies viewed in, or close to, edge-on projection, as well as in the Milky Way. They are the product of dynamical instabilities occurring in stellar bars, which cause the latter to buckle and thicken vertically. Recent studies have found nearby galaxies that harbour two such features arising at different radial scales, in a nested configuration. In this paper, we explore the formation of such double peanuts, using a collisionless N-body simulation of a pure disc evolving in isolation within a live dark matter halo, which we analyse in a completely analogous way to observations of real galaxies. In the simulation, we find a stable double configuration consisting of two X/peanut structures associated with the same galactic bar – rotating with the same pattern speed – but with different morphology, formation time, and evolution. The inner, conventional peanut-shaped structure forms early via the buckling of the bar, and experiences little evolution once it stabilizes. This feature is consistent in terms of size, strength, and morphology, with peanut structures observed in nearby galaxies. The outer structure, however, displays a strong X, or ‘bow-tie’, morphology. It forms just after the inner peanut, and gradually extends in time (within 1–1.5 Gyr) to almost the end of the bar, a radial scale where ansae occur. We conclude that, although both structures form, and are dynamically coupled to, the same bar, they are supported by inherently different mechanisms.

Sponsoring Organization:
USDOE
OSTI ID:
1772843
Journal Information:
Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 2 Vol. 503; ISSN 0035-8711
Publisher:
Oxford University PressCopyright Statement
Country of Publication:
United Kingdom
Language:
English

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