Map of the large-scale emission as measured by the ¹³CO 1–0 line. The map covered by [C i] observations is shown as gray rectangle in the centre, the brown rectangles around that map indicate the locations of the OFF maps taken in the double beam-switch scheme at the different times and dates of the observations. The circle indicates the size of the KOSMA error beam at the [C i] frequency. The FCRAO error beam at the ¹³CO 1–0 frequency is smaller by a factor three and is not shown here.