1996A&A...305..592W

In our line and continuum data base of the Cygnus X region we found a particularly strong continuum absorption in the 21-cm HI line against the HII region DR 7. After deriving the expected emission line from the surrounding emission distribution we calculate optical depth and spin temperature curves as a function of radial velocity (or distance). The fact that the continuum source and the absorption structures are spatially resolved can be used for several independent consistency checks and turns out to be an advantage contrarily to common belief. HI in the local spiral arm apparently has an optical depth close to 1.5 and a spin temperature around 140K. Beyond, e.g. from 4 to 7kpc distance structures in the distribution of both quantities can be seen. It is suggested that future data bases like the planned DRAO galactic plane survey could contain many lines of sight where these parameters could be studied in great detail.