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CO+, HCO+ Imaging and Outflows: Mapping NGC 7027 in New Light

Presentation #507.03 in the session “Planetary Nebulae, Supernova Remnants”.

Published onJan 11, 2021
CO+, HCO+ Imaging and Outflows: Mapping NGC 7027 in New Light

The class of molecule-rich planetary nebulae (PNe) serve as excellent subjects to understand the effects of high-energy radiation on molecular chemistry in photon-dominated regions (PDRs) and X-ray-dominated regions (XDRs). We present results from the first stage of our interferometric spectral line mapping of the young and rapidly evolving planetary nebula NGC 7027, whose massive molecular envelope is strongly irradiated by a hot, UV-bright central star and luminous, diffuse X-rays from strong shocks. We have obtained the first map of the molecular ion CO+ in NGC 7027, as well as a complementary 2"-resolution map of HCO+. Analysis of these IRAM NOEMA interferometer data reveal distinct emission structures for CO+ and HCO+, indicative of PDR-driven and XDR-driven chemistries, respectively. While CO+ is found to precisely trace near-IR H2 emission, comparison of the CO+ and HCO+ maps reveals a clear spatial displacement between the two molecules, with the regions of greatest HCO+ density, along the central waist of the nebula, offset outward from those of CO+ by ~1000 au. The velocity channel maps of HCO+ are compared with recently obtained HST/WFC3 images (Moraga et al., this meeting) to ascertain the geometry of NGC 7027’s complex system of collimated, fast, X-ray-generating outflows.

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