The protostellar jet driven by L1448C was observed in the SiO J =8–7 and CO J =3–2 lines and 350 GHz dust continuum at \sim 1″resolution with the Submillimeter Array ( SMA ) .
A narrow jet from the northern source L1448C ( N ) was observed in the SiO and the high-velocity CO .
The jet consists of a chain of emission knots with an inter-knot spacing of \sim 2″ ( 500 AU ) and a semi-periodic velocity variation .
These knots are likely to be the internal bow shocks in the jet beam that were formed due to the periodic variation of the ejection velocity with a period of \sim 15—20 yr .
The innermost pair of knots , which are significant in the SiO map but barely seen in the CO , are located at \sim 1″ ( 250 AU ) from the central source , L1448C ( N ) .
Since the dynamical time scale for the innermost pair is only \sim 10 yr , SiO may have been formed in the protostellar wind through the gas-phase reaction , or been formed on the dust grain and directly released into the gas phase by means of shocks .
It is found that the jet is extremely active with a mechanical luminosity of \sim 7 L _ { \odot } , which is comparable to the bolometric luminosity of the central source ( 7.5 L _ { \odot } ) .
The mass accretion rate onto the protostar derived from the mass-loss rate is \sim 10 ^ { -5 } M _ { \odot } yr ^ { -1 } .
Such a high mass accretion rate suggests that the mass and the age of the central star are 0.03–0.09 M _ { \odot } and ( 4–12 ) \times 10 ^ { 3 } yr , respectively , implying that the central star is in the very early stage of protostellar evolution .
The low-velocity CO emission delineates two V-shaped shells with a common apex at L1448C ( N ) .
The kinematics of these shells are reproduced by the model of a wide opening angle wind .
The co-existence of the highly-collimated jets and the wide-opening angle shells can be explained by the “ unified X -wind model ” in which highly-collimated jet components correspond to the on-axis density enhancement of the wide-opening angle wind .
The CO J =3–2 map also revealed the second outflow driven by the southern source L1448C ( S ) located at \sim 8.3″ ( 2000 AU ) from L1448C ( N ) .
Although L1448C ( S ) is brighter than L1448C ( N ) in the mid-IR bands , the momentum flux of the outflow from L1448C ( S ) is two or three orders of magnitude smaller than that of the L1448C ( N ) outflow .
It is likely that the evolution of L1448C ( S ) has been strongly affected by the powerful outflow from L1448C ( N ) .