Molecular observations of four planetary nebulae (PNe), M4-17, Hu 1-1, M1-59, and Na 2, were conducted at 1–3 mm using the Arizona Radio Observatory’s 12 m antenna and Submillimeter Telescope, and the Institut de Radioastronomie Millimétrique 30 m Telescope. Toward M4-17, HNC (
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Abstract J = 3 → 2), CCH (N = 2 → 1,N = 3 → 2), CN (N = 1 → 0,N = 2 → 1), H2CO (J Ka,Kc= 21,2→ 11,1,J Ka,Kc= 20,2→ 10,1,J Ka,Kc= 21,1→ 11,0), CS (J = 3 → 2,J = 5 → 4), and H13CN (J = 2 → 1) were detected. An almost identical set of transitions was identified toward Hu 1-1. Moreover, c–C3H2was detected in Hu 1-1 via three 2 mm lines:J Ka,Kc= 31,2→ 22,1,J Ka,Kc= 41,4→ 30,3, andJ Ka,Kc= 32, 2→ 21,1. HNC, CCH, CN, CS, and H13CN were found in M1-59, as well as H2S via itsJ Ka,Kc= 11,0→ 10,1line—the first detection of this key sulfur species in PNe. In addition, CCH and CN were identified in the 27,000 yr old Na 2. Among these four sources, CN and CCH were the most prevalent molecules (after CO and H2) with fractional abundances, relative to H2, off ∼ 0.9–7.5 × 10−7and 0.8–7.5 × 10−7, respectively. CS and HNC have abundances in the rangef ∼ 0.5–5 × 10−8, the latter resulting in HCN/HNC ∼ 3 across all three PNe. The unusual species H2CO, c–C3H2, and H2S hadf ∼ 3–4 × 10−7, 10−8, and 6 × 10−8. This study suggests that elliptical PNe such as Hu 1-1 can have a diverse molecular composition. The presence of CN, CCH, and HCO+in Na 2, with comparable abundances to younger PNe, demonstrates that molecular content is maintained into the late PN stage. -
Abstract The
J = 5.5 → 4.5 andJ = 5 → 4 transitions of PO and PN, respectively, have been imaged in the envelope of hypergiant star VY Canis Majoris (VY CMa) using the Atacama Large Millimeter/submillimeter Array with angular resolutions of 0.″2 and 1.″5 and data from the Submillimeter Telescope of the Arizona Radio Observatory. These maps are the first high-fidelity images of PO and PN in a circumstellar envelope. Both molecules are primarily present in a spherical, star-centered region with a radius ∼60R *(0.″5), indicating formation by LTE chemistry and then condensation into grains. PN, however, shows additional, fan-shaped emission 2″ southwest of the star, coincident with dust features resolved by Hubble Space Telescope (HST), as well as four newly identified distinct structures 1″–2″ toward the north, east, and west (Cloudlets I–IV), not visible in HST images. The “SW Fan” and the cloudlets are also prominent in theJ = 5.5 → 4.5 transition of NS. The correlation of PN with NS, SiO, and dust knots in the SW Fan suggests a formation in shocked gas enhanced with nitrogen. Excess nitrogen is predicted to favor PN synthesis over PO. Abundances for PN and PO in the spherical source aref ∼ 4.4 × 10−8and 1.4 × 10−7, respectively, relative to H2. Given a cosmic abundance of phosphorus, an unusually high fraction (∼35%) is contained in PO and PN. Alternatively, the stellar winds may be enriched in P (and N) by dredge-up from the interior of VY CMa.