The neutral-hydrogen distribution in the region of the radio source CygnusX

The HI distribution in the region of the radio source Cygnus X and the supe rnova remnant G78.2+2.1 has been investigated using observations in the 21- cm radio line with an angular resolution of 2.4' obtained on the RATAN-600 radio telescope. Two HI shells can be distinguished: the first (diameter ap proximate to 7 degrees) surrounds the entire extended thermal radio source Cygnus X, while the second, smaller, one (diameter approximate to 2 degrees ) envelops the supernova remnant. Both shells display expansion with veloci ties exceeding 10 km/s. To compare the HI and ionized-gas velocities, the r egion was observed in the H-alpha line with a Fabry-Perot interferometer an d CCD array on the 125-cm telescope of the Crimean Laboratory of the Sternb erg Astronomical Institute. The molecular-gas distribution around Cygnus X is considered on the basis of the CO line emission. The physical parameters of HI shells are determined, and their nature is discussed. The presence o f a large HI shell and a cavity in the molecular-gas distribution around Cy gnus X indicates that the radio source may form a single structure. The sma ller HI shell around G78.2+2.1 could have been created by either the supern ova explosion or the stellar wind of the precursor star.