The Detection of super(3)He super(+) in a Planetary Nebula Using the VLA

We used the VLA to search for super(3)He super(+) emission from two Galactic planetary nebulae (PNe): NGC 6572 and J320. Standard stellar models predict that the super(3)He/H abundance ratios for PNe should be 1-2 orders of magnitude higher than the primordial value ( super(3)He/H 6 10 super(-5) by number) determined from Galactic H II region abundances and confirmed by WMAP cosmic microwave background results. Chemical evolution models suggest that fewer than 5% of all PNe enrich the interstellar medium (ISM) with super(3)He at the level of standard stellar models. Our target PNe are therefore anomalous in that they were selected from a sample deliberately biased to contain objects with properties that maximized the likelihood of a super(3)He detection by the VLA. We have detected the 8.665 GHz hyperfine super(3)He super(+) transition in J320 at the 4 s level. The super(3)He/H abundance ratio is 1.9 x 10 super(-3) with roughly a factor of 2 uncertainty. For NGC 6572 we find an upper limit of super(3)He/H 10 super(-3). This detection of super(3)He in J320 makes it the second PN known to have an anomalously high super(3)He abundance, confirming that at least some low-mass stars produce significant amounts of super(3)He that survives to the PN stage and enriches the ISM.