First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418
Abstract
The 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. He abundances in PNe can help test models of the chemical evolution of the Galaxy. We present the detection of the He emission line using the single dish Deep Space Station 63, towards the PN IC418. We derived a He/H abundance in the range 1.740.810 to 5.81.710, depending on whether part of the line arises in an outer ionized halo. The lower value for He/H ratio approaches values predicted by stellar models which include thermohaline mixing, but requires that large amounts of He are produced inside low-mass stars which enrich the interstellar medium (ISM). However, this over-predicts the He abundance in HII regions, the ISM, and proto-solar grains, which is known to be of the order of 10. This discrepancy questions our understanding of the evolution of the He, from circumstellar environments to the ISM.
Keywords
Cite
@article{arxiv.1604.02679,
title = {First Detection of $^3$He$^+$ in the Planetary Nebula IC$\,$418},
author = {L. Guzman-Ramirez and J. R. Rizzo and A. A. Zijlstra and C. García-Miró and C. Morisset and M. D. Gray},
journal= {arXiv preprint arXiv:1604.02679},
year = {2016}
}
Comments
5 pages, 4 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society Letters