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 [Fe II] lines in the J- and H-bands. While the visual-extinction estimated from the [Fe II] line ratios reaches more than 20 mag in the close vicinity of IRS 5, it decreases rapidly at similar to 1 " from 1RS 5 and remains constant around 7 mag at larger distances. The electron density in the jets is estimated to be 10(6) cm(-3) near IRS 5 and is 10(4) to 10(5) 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.