Abstract
Collimated outflows and jets play a critical role in shaping planetary nebulae (PNe), especially in the brief transition from a spherical AGB envelope to an aspherical PN, which is called the protoplanetary nebula (pPN) phase. We present UV observations of Hen 3-1475, a bipolar pPN with fast, highly collimated jets, obtained with STIS on board the Hubble Space Telescope (HST). The deep, low-dispersion spectroscopy enabled monochromatic imaging of Hen 3-1475 in different UV nebular emission lines; this is the first of such attempt ever conducted for a pPN. The northwest inner knot (NW1) is resolved into four components in Mg ii λ 2800. Through comparison analysis with the HST optical narrowband images obtained 6 yr earlier, we found that these components of NW1 hardly move, despite of a negative gradient of high radial velocities, from −1550 km s - 1 on the innermost component to ∼−300 km s - 1 on the outermost. These NW1 knot components might thus be quasi-stationary shocks near the tip of the conical outflow of Hen 3-1475.
Highlights
Hen 3-1475 (a.k.a., the “Garden Sprinkler Nebula”; IRAS 17423-1755) is known to harbour very fast bipolar outflows [1]
Long-slit UV spectra of Hen 3-1475 were obtained with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST) on 11 June 2015
Grating is ∼310 km s−1, which can be set as an upper-limit approaching speed of the outermost component D
Summary
Hen 3-1475 (a.k.a., the “Garden Sprinkler Nebula”; IRAS 17423-1755) is known to harbour very fast bipolar outflows [1]. Since its nature as a protoplanetary nebula (pPN) was settled, Hen 3-1475 has been imaged several times [2,3,4,5]. It has a highly collimated bipolar structure with an S-shaped string of point-symmetric, [N II]-bright knots extending over ∼1700 along the main axis (Figure 1). IUE detection of UV emission lines in Hen 3-1475 was only marginal due to dust obscuration [10]. This proceeding paper reports the first UV spectroscopy of Hen 3-1475 with high spatial resolution
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