Comparison of the [C ii] position-velocity strip scans with the AST/RO observations of [C i] and CO(4–3) (Martin et al. 2004). a) The [C ii] longitude-velocity strip scan and b) the latitude-velocity strip scan. The [C i] and CO maps are shown in gray scale, where the grey scale bars on the right hand side indicate the main beam temperatures, T_mb(K); the corresponding [C ii]  emission maps are overlaid as contours. The [C ii] contour levels (red) are T_mb(K) = 1, 2, 4, 6, 8, and 10. In the l-V maps the dashed line roughly outlines the [C ii]  emission at b = 0.̊0 for the elliptical ring model of Molinari et al. (2011; see also Fig. 2). This ellipse is used only to delineate the l-V space where the open orbit gas streams can be found, and is not intended as a model of the gas dynamics. The arrows in panel b) indicate a local H ii source (see Sect. 4.8).