Pulsed jet as the source of momentum in bipolar molecular outflows

It is proposed that freely falling material inflates and squeezes a hot cavity in the center of an accretion disk, thereby creating a momentum reservoir at the free-fall pressure. The heated, light material rises through the more dense confining axial accretion, becoming a stellar jet by the usual nozzle mechanism. This can solve the momentum problem in the bipolar molecular outflows, because the free-fall pressure head can drive a momentum flux much in excess of the radiative momentum flux. In fact, the momentum flux produced by this mechanism can be about 100 times larger than the radiative flux from the central source for both high and low-luminosity molecular outflow sources, when the cavity radius is about 100 times the stellar radius and the accretion shock temperature is 10 to the 6.3 K. The asymptotic jet velocity is 370 km/s for these parameters. The model suggests a quasi-continuous outflow (a pulsed jet) associated with the larger scale bipolar molecular outflow due to a relaxation oscillation with a 50 percent duty cycle. The period of the oscillator is essentially twice the free-fall time from the cavity radius. The jet phase may be associated with soft X-rays concentrated along the axis of the jet. This model may also apply to active galactic nuclei. 22 references