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arXiv · 1604.02679

First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418

L. Guzman-Ramirez·J. R. Rizzo·A. A. Zijlstra·C. García-Miró·C. Morisset·M. D. Gray
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Abstract

The $^3$He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in low-mass stars which evolve through the planetary nebula (PN) phase. $^3$He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the $^3$He$^+$ emission line using the single dish Deep Space Station 63, towards the PN IC$\,$418. We derived a $^3$He/H abundance in the range 1.74$\pm$0.8$\times$10$^{-3}$ to 5.8$\pm$1.7$\times$10$^{-3}$, depending on whether part of the line arises in an outer ionized halo. The lower value for $^3$He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of $^3$He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this over-predicts the $^3$He abundance in HII regions, the ISM, and proto-solar grains, which is known to be of the order of 10$^{-5}$. This discrepancy questions our understanding of the evolution of the $^3$He, from circumstellar environments to the ISM.

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L. Guzman-Ramirez, J. R. Rizzo, A. A. Zijlstra, C. García-Miró, C. Morisset, M. D. Gray. 2016-04-10. First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418. https://doi.org/10.1093/mnrasl/slw070

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