HST STIS observations of the mixing layer in the Cat's Eye Nebula

Abstract

Planetary nebulae (PNe) are expected to have a ~10${}^5$ K interface layer between the $\ge$10${}^6$ K inner hot bubble and the ~10${}^4$ K optical nebular shell. The PN structure and evolution, and the X-ray emission depend critically on the efficiency of mixing of material at this interface layer. However, neither its location nor its spatial extent has ever been determined so far. Using high-spatial resolution HST STIS spectroscopic observations of the N V 1239,1243 lines in the Cat's Eye Nebula (NGC 6543), we have detected this interface layer and determined its location, extent, and physical properties for the first time in a PN. We confirm that this interface layer, as revealed by the spatial distribution of the N V 1239 line emission, is located between the hot bubble and the optical nebular shell. We estimate a thickness of 1.5$\times$10${}^{16}$ cm and an electron density of ~200 cm${}^{-3}$ for the mixing layer. With a thermal pressure of ~2$\times$10${}^{-8}$ dyn cm${}^{-2}$, the mixing layer is in pressure equilibrium with the hot bubble and ionized nebular rim of NGC 6543.

Accepted for publication in the ApJ Letters; five pages, including 1 table and 3 figures

References in corpus (7)

• The Effelsberg-Bonn HI Survey: Milky Way gas. First data release
• Million-Degree Plasma Pervading the Extended Orion Nebula
• The Chandra Planetary Nebula Survey (ChanPlaNS). II. X-ray Emission from Compact Planetary Nebulae
• Formation and X-ray emission from Hot Bubbles in Planetary Nebulae. I. Hot Bubble formation
• Independent Emission and Absorption Abundances for Planetary Nebulae
• NLTE Model of NGC 6543's Central Star and its Relation with the Surrounding Planetary Nebula
• Structure and clumping in the fast wind of NGC6543

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• Chandra observations of the planetary nebula IC 4593
• Planetary nebulae with Wolf-Rayet-type central stars -- IV. NGC 1501 and its mixing layer