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Astron. Astrophys. 345, 787-812 (1999)

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3D self-consistent N-body barred models of the Milky Way

II. Gas dynamics

R. Fux

Geneva Observatory, Ch. des Maillettes 51, CH-1290 Sauverny, Switzerland

Received 26 November 1998 / Accepted 5 February 1999


The gas dynamics in the Galactic disc is modeled by releasing an initially axisymmetric SPH component in a completely self-consistent and symmetry-free 3D N-body simulation of the Milky Way in which the stellar components display a COBE-like bar. The density centre of the stellar bar wanders around the centre of mass and the resulting gas flow is asymmetric and non-stationary , reproducing the HI and CO [FORMULA] diagrams only at specific times and thus suggesting a transient nature of the observed inner gas kinematics.

The best matching models allow a new and coherent interpretation of the main features standing out of the [FORMULA] data within the bar region. In particular, the [FORMULA] traces of the prominent offset dustlanes leading the bar major axis in early-type barred spirals can be unambiguously identified, and the 3-kpc arm and its non-symmetric galactocentric opposite counterarm are the inner prolongations of disc spiral arms passing round the bar and joining the dustlanes at very different galactocentric distances. Bania's clump 1 and 2, and another velocity-elongated feature near [FORMULA], are interpreted as gas lumps crossing the dustlane shocks. The terminal velocity peaks near [FORMULA] are produced by gas along the dustlanes and not by the trace of the cusped [FORMULA] orbit, which passes farther away from the Galactic centre. According to these models and to related geometrical constraints, the Galactic bar must have an inclination angle of [FORMULA], a corotation radius of [FORMULA] kpc and a face-on axis ratio [FORMULA].

Key words: Galaxy: structure – Galaxy: kinematics and dynamics – ISM: kinematics and dynamics – Galaxy: center – hydrodynamics – methods: numerical

Send offprint requests to: R. Fux

Correspondence to: Roger.Fux@obs.unige.ch

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© European Southern Observatory (ESO) 1999

Online publication: April 28, 1999