HST STIS UV Spectroscopic Observations of the Protoplanetary Nebula Hen3-1475

Abstract

We present UV spectra of the protoplanetary nebula (pPN) Hen 3-1475 obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). Our deep, low-dispersion spectroscopy enables monochromatic imaging of Hen 3-1475 in ultraviolet (UV) nebular emission lines, the first of such attempt ever made for a pPN. The high spatial resolution of STIS imaging allows an unprecedentedly sharp view of the S-shaped jet, especially the inner NW1 knot, which is resolved into four components in Mg II λ2800. Through critical comparison with HST optical narrowband images, we found a negative radial velocity gradient in NW1, from -1550 km s^-1 on its innermost component to ∼-300 km s^-1 on the outermost. Despite their high radial velocities, these components of NW1 mostly show no obvious (or very small) proper motions, indicating that they might be quasi-stationary shocks near the tip of the conical flow along the collimated jet of Hen 3-1475.