THE FORMATION OF STELLAR-SYSTEMS BY GRAVITATIONAL-INSTABILITY IN THE CYGNUS SUPERBUBBLE

We have developed an analytical model of the onset of gravitational instabilities in the dense shell surrounding an expanding superbubble, in order to account for the origin of Cygnus OB1-OB9 and the anomalous motion of the stars in that region as reported in a previous paper. Expressions for the masses, sizes, and ages for the resulting unstable complexes are derived, the observed peculiar velocity in Cygnus OB1-OB9 being used as an input parameter. It is shown that the mechanical luminosity injected into the Cygnus Superbubble by stellar winds in the active association Cygnus OB2 is consistent with the observational characteristics of Cygnus OB1-OB9, if Cygnus OB2 was originally immersed in an ISM dominated by giant molecular complexes.