Top: cumulative absorbing column density (solid line) as a function of radial velocity at the position of highest X-ray absorption (see Sect. 4.3). The relative contributions from the atomic and molecular hydrogen are represented by the dashed and dash-dotted lines respectively. Middle: rotation curve towards the same direction as derived from the model of Galactic rotation of Hou et al. (2009). Bottom: ¹²CO (dashed line) and HI (dash-dotted line) spectra obtained the region highest X-ray absorption.