A Pair of Twisted Jets of Ionized Iron from L 1551 IRS 5

High-resolution near-infrared J-band imaging with the Subaru Telescope has demonstrated, for the first time from the ground, two independent jets emanating from the protostar L 1551 IRS 5. Successive near-infrared spectroscopy has revealed that the jet emission is dominated by [FeII] lines in the J- and H-bands. While the visual-extinction estimated from the [FeII] line ratios reaches more than 20 mag in the close vicinity of IRS 5, it decreases rapidly at ∼ 1″ from IRS 5 and remains constant around 7 mag at larger distances. The electron density in the jets is estimated to be 10⁶ cm⁻³ near IRS 5 and is 10⁴ to 10⁵ cm⁻³ in their outer section. The twisted appearance of the jets, with bright knots especially prominent in the northern jet, is similar to the R-band jets observed with the Hubble Space Telescope. These results suggest that the twisted structure and bright emission knots are intrinsic to the jets and are not due to a spatial variation of the extinction.