Supershells and propagating star formation
R. McCray, M. Kafatos;
ApJ, 1987, 317, 190
ABSTRACT:Stellar winds and repeated supernovae from an OB association will create a cavity of coronal gas in
the interstellar medium, with radius greater than 100 pc, surrounded by a
dense, expanding shell of cool interstellar gas.
If the association has a
typical initial mass function, its supernovae explosions will inject energy
into the supershell at a nearly constant rate for about 50 Myr.
The
supershell loses its interior pressure and enters the snowplow phase when
radiative cooling becomes important or when the shell bursts through the gas disk
of a galaxy, typically after a few times 10 Myr and with a radius of 100-300
pc.
At approximately the same time, the supershell becomes gravitationally
unstable, forming giant molecular clouds which are sites for new star
formation.
There is widespread evidence for supershells in the Galaxy and other spiral
and irregular galaxies from 21-cm emission-line surveys, optical
emission-line surveys, and studies of supernova remnants.
The gravitational
instability of the supershells provides a physical mechanism for induced star
formation and may account for bursts of star formation, especially in irregular
galaxies.
KEYWORDS: interstellar matter, star formation, stellar envelopes, stellar coronas, stellar winds, supernovae
PERSOKEY:supershell, ,
CODE: mccray87