We have obtained narrowband images of the young planetary nebula Hubble 12 showing [Fe II] line emission in bipolar bubbles near the core. Bright [Fe II] emission is strong evidence for shocks, suggesting the presence of a high-velocity wind emanating from the central star. We compare our data to previously published images of Hubble 12 - finding similar structures in hydrogen recombination and free-free emission - and we propose three possible interpretations of the data: that the bubbles indicate the inner shock of the fast wind, that the [Fe II) emission is evidence of the outer shock of an episodic wind, or that the emission is cooling line radiation from a photodissociation region. We argue that the first two interpretations are more likely, since the [Fe II] emission must be shock excited.
Bibliographical noteFunding Information:
The authors extend their gratitude to Joseph Hora for providing the H2 emission image of Hubble 12, to Bruce Balick and Garrelt Mellema for stimulating discussions, and to Margaret Meixner for her timely and valuable contributions as this Letter’s referee. Infrared astronomy at the University of Rochester is supported by grants from the NSF and NASA and by contributions from the Astronomical Society of New York. A. F. acknowledges financial support from NSF grant AST 97-8765, and C. E. W. from NSF grant AST 94-53354.
- Jets and outflows planetary nebulae: Individual (Hb 12)
- Stars: Evolution