How axi-symmetric is the inner HI disc of the Milky Way?

Abstract

We modelled the distribution and the kinematics of HI in the inner Milky Way (R<Rsun) at latitude b=0° assuming axi-symmetry. We fitted the line profiles of the LAB 21-cm survey using an iterative approach based on the tangent-point method. The resulting model reproduces the HI data remarkably well, with significant differences arising only for R<2 kpc. This suggests that, despite the presence of a barred potential, the neutral gas in the inner Milky Way is distributed in a fairly axi-symmetric disc.

2 pages, 3 figures, to appear in the proceedings of "Assembling the Puzzle of the Milky Way", Le Grand Bornand (Apr. 17-22, 2011)