SUBARU High‐Dispersion Spectroscopy of Hα and [N ii ] 6583 Å Emission in the HH 46/47 Jet

Abstract

We present slit-scan observations of the Hα and [N II] 6583 Å emission lines toward the HH 46/47 jet with the Subaru Telescope. The spectral resolution of R = 3.6 × 104 allowed us to study the kinematics of individual features in unprecedented detail. The spectra show (1) the main jet component (VL ∼ -160 km S-1), which is seen in both Ha and [N II] emission, and (2) distinct lower velocity components (|V LSR| &≲ 120 km s-1), which are clearly seen in Ha but are marginal or absent in [N II], The measured [N II]/Hα ratios are 0.2-0.5 and <0.2 (typically <0.1) in these two components, respectively. The velocities of the Ha and [N II] emission in the main jet component match each other well, suggesting that these are associated with the ejecta. The low-velocity components are associated with one-sided bow shocks and an Hα filament, where the jet interacts with the ambient gas. The line profiles at the bow shocks and the Ha filament suggest that the surrounding gas moves outward by ∼200 km s_1 due to prompt entrainment. The difference in excitation conditions between the two velocity components is explained if the preshock gas is partially ionized in the main jet component, at the apices of the bow shocks and the Ha filaments, while the ambient gas is almost neutral. © 2008. The American Astronomical Society. All rights reserved.