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Abstract We present Submillimeter Array (SMA) mapping of12COJ= 2 → 1,13COJ= 2 → 1, and CNN= 2 → 1 emission from the ring-like planetary nebula NGC 3132, one of the subjects of JWST Early Release Observation near-infrared imaging. The ∼5″ resolution SMA data demonstrate that the Southern Ring’s main, bright, molecule-rich ring is indeed an expanding ring, as opposed to a limb-brightened shell, in terms of its intrinsic (physical) structure. This suggests that NGC 3132 is a bipolar nebula viewed more or less pole-on (inclination ∼15°–30°). The SMA data furthermore reveal that the nebula harbors a second expanding molecular ring that is aligned almost orthogonally to the main, bright molecular ring. We propose that this two-ring structure is the remnant of an ellipsoidal molecular envelope of ejecta that terminated the progenitor star’s asymptotic giant branch evolution and was subsequently disrupted by a series of misaligned fast, collimated outflows or jets resulting from interactions between the progenitor and one or more companions.
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This content will become publicly available on February 25, 2026
The Structure of the Molecular Envelope of the Ring Nebula (NGC 6720)
Abstract We present the first interferometric imaging of molecular line emission from the Ring Nebula, NGC 6720, in the form of Submillimeter Array (SMA) observations of COJ = 2 → 1 emission. The SMA12CO(2–1) mapping data, with ∼3″ spatial resolution and 2 km s−1velocity resolution, provide an unprecedentedly detailed, 3D view of the Ring’s clumpy molecular envelope. The emission morphology displayed in the velocity-integrated SMA12CO(2–1) image closely resembles the morphologies of near-IR H2and polycyclic aromatic hydrocarbon emission as revealed in recent JWST/NIRCam imaging of NGC 6720. The SMA12CO(2–1) data demonstrate that the molecular gas is found within a geometrically thin layer that immediately surrounds the ionized gas imaged by Hubble Space Telescope and JWST. A simple, geometric model of the12CO(2–1) emission data shows that the intrinsic structure of NGC 6720’s molecular envelope closely resembles a truncated, triaxial ellipsoid that is viewed close to pole-on, and that the dynamical age of the molecular envelope is ∼6000 yr. The SMA12CO(2–1) mapping data furthermore reveal that some of the faint, filamentary features seen projected in the Ring’s interior in JWST imaging are in fact fast-moving polar knots or bullets with radial velocities of ±45–50 km s−1relative to the systemic velocity, and that the hot progenitor star remnant is positioned at the precise geometric center of the clumpy, ellipsoidal molecular shell. We assert that the Ring’s molecular envelope represents the “fossil” remnant of a relatively sudden mass ejection ∼6000 yr ago that terminated the progenitor star’s asymptotic giant branch (AGB) evolution, and that this ellipsoidal envelope of AGB ejecta was then punctured by fast, collimated polar outflows or jets resulting from interactions between the progenitor and one or more companion stars. Such an evolutionary scenario may describe most if not all molecule-rich, “Ring-like” planetary nebulae.
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- Award ID(s):
- 2206033
- PAR ID:
- 10643261
- Publisher / Repository:
- AAS Journals
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 981
- Issue:
- 1
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 46
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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