Neutral oxygen in planetary nebulae - Probing radiative transfer and nebular structure

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Astrophysical Journal; (United States)

DOI:https://doi.org/10.1086/170348· OSTI ID:5157220

Richer, M G; Mccall, M L; Martin, P G ^[1]

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1. Toronto, University (Canada) York University, North York (Canada) Canadian Institute for Theoretical Astrophysics, Toronto (Canada)

For the first time, forbidden O I 5577 A and forbidden O I 6364 A have together been mapped across planetary nebulae, making possible direct measurement of transition zone temperatures. In NGC 2440, the neutral oxygen temperature is 10,400 {plus minus} 600 K, compared with 10,200 {plus minus} 200 K for the forbidden N II temperature and 14,100 {plus minus} 300 K for the forbidden O III temperature. The forbidden O I temperature in NGC 3918 is 13,000 {plus minus} 900 K, significantly different from that in NGC 2440. Models computed with the nebula code CLOUDY successfully reproduce the forbidden O I and forbidden O III temperatures observed in NGC 2440, indicating that the implemented blend of on-the-spot and outward-only approximations to the transfer of diffuse radiation is a reasonable representation of reality. Even though radiation hardening enhances the heating at large optical depths within a planetary nebula, an increase in the cooling efficiency can present a concomitant rise in temperature. It is predicted that hot transition zones, as observed in NGC 3918, should be restricted to nebulae with cooler central stars and metal abundances (particularly N) at or below solar. 48 refs.

• OSTI ID: 5157220
• Journal Information: Astrophysical Journal; (United States), Journal Name: Astrophysical Journal; (United States) Vol. 377; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHEMICAL COMPOSITION
ELEMENTS
ENERGY-LEVEL TRANSITIONS
FORBIDDEN TRANSITIONS
HEATING
MASS
MATHEMATICAL MODELS
MORPHOLOGY
NEBULAE
NONMETALS
OXYGEN
PLANETARY NEBULAE
RADIATION TRANSPORT
STAR MODELS
TEMPERATURE MEASUREMENT