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Extreme Active Molecular Jets in L1448C

圖片來源: Hirano et al.

Distributions of the high velocity SiO (left panel) and CO (right) emission. The velocity ranges are ±51–70km s with respect to the systemic velocity. Green cross in each panel denotes the position of the continuum peak of L1448C(N).

The protostellar jet driven by L1448C was observed in the SiO (8–7) and CO (3–2) lines at ~1" resolution with the SMA. A narrow jet from the northern source L1448C(N) was observed in the SiO and the high-velocity CO emission. The jet consists of a chain of emission knots with an inter-knot spacing of ~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 ~15–20 yr. It is found that the jet is extremely active with a mechanical luminosity of ~7 L☉, which is comparable to the luminosity of the central source (~ 7.5 L☉). The mass accretion rate onto the protostar derived from the mass-loss rate is ~10-5 M☉ 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☉ and (4–12) × 103 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. (Hirano et al. 2010, ApJ, 717, 58)