Аннотация
ABSTRACT A new high-sensitivity survey of 6 cm $\rm H_2CO$ $(1_{1,0}$–$1_{1,1})$ absorption and ${\rm H110} \, \alpha$ emission confirms the widespread molecular structures in the Cygnus-X region. High formaldehyde column densities identify regions with ongoing or new star formation activity, while the hydrogen recombination emission reveals past and evolved star formation regions. A novel method has been introduced to estimate the H$_2$CO excitation temperature $T_{\rm ex}$ of the Cygnus-X region using only the 6 cm transition that resulting in an updated map of the excitation temperature field. The excitation temperatures and the associated background temperatures in the Cygnus-North region confirm the star formation activity in Cygnus-North to be higher than in Cygnus-South. The $\rm H_2CO$ absorption contours and the ${\rm H110} \, \alpha$ contours show some association with the 6 cm continuum structure and reveal a complex structure of current and past star formation regions. The formaldehyde line proves to be an excellent tracer of existing and future star formation regions.