Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

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Appendices A-C are only available in electronic form at http://www.aanda.org

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... bar

Note that although this conclusion drawn from the elliptical orbit model was used as an hypothesis to fix some of the parameters of the potential, these fixed parameters are not related to the bar position angle, so the argument is not circular.

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... eye

This comparison uses the DALIA interface to numerical simulation codes which is being developed jointly by the Observatoire de Paris and the Max Planck Institut Für Radioastronomie (Boone et al. 2006). This graphical user interface gives access to the model parameters and allows the user to directly compare the outputs of the code with real observations.

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