Adaptive Optics Spectroscopy of the [Fe II] Outflows from HL Tauri and RW Aurigae

Abstract

We present new results of [Fe II] 1.644-micron spectroscopy toward the jets from HL Tau and RW Aur carried out with the Subaru Telescope combined with the adaptive optics system. We observed the regions within 2" - 3" from the stars with the sub-arcsecond resolutions of 0."5 and 0."2 for HL Tau and RW Aur, respectively. In addition to the strong, high velocity emission extended along each jet, we detected a blueshifted low velocity emission feature seen as a wing or shoulder of the high velocity emission at each stellar position. Detailed analysis shows that the position-velocity diagrams (PVDs) of HL Tau and RW Aur show a characteristic similar to those of the cold disk wind and X-wind models in that the [Fe II] line width is broad in the vicinity of the stellar position and is narrower at the extended jet. A closer comparison suggests, however, that the disk wind model tends to have too large line width at the jet while the X-wind model has excess emission on the redshifted side at the stellar position. The narrow velocity width with symmetric line profiles of the observed high velocity emission supports an X-wind type model where the launching region is localized in a small radial range, while the low velocity emission located away from the star favors the presence of a disk wind. The [Fe II] emission from the HL Tau jet shows a gap of 0."8 between the redshifted jet and the star, indicating the presence of an optically thick disk of ~ 160 AU in radius. The [Fe II] emission from the RW Aur jet shows a marked drop from the redshifted peak at Y ~ -0."2 toward the star, suggesting that its disk radius is smaller than 40 AU.