The Herschel Planetary Nebula Survey (HerPlaNS): A Comprehensive Dusty Photoionization Model of NGC6781

Journal Article · Tue Aug 01 04:00:00 EDT 2017 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.3847/1538-4365/AA8175· OSTI ID:22872564

Otsuka, Masaaki; Chu, You-Hua ^[1]; Ueta, Toshiya ^[2]; Hoof, Peter A. M. van ^[3]; Sahai, Raghvendra ^[4]; Aleman, Isabel ^[5]; Zijlstra, Albert A. ^[6]; Villaver, Eva ^[7]; Leal-Ferreira, Marcelo L. ^[8]; Kastner, Joel ^[9]; Szczerba, Ryszard ^[10]

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1. Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU. No.1, Section 4, Roosevelt Rd., Taipei 10617, Taiwan, ROC (China)
2. Department of Physics and Astronomy, University of Denver, 2112 E. Wesley Ave., Denver, CO 80210 (United States)
3. Royal Observatory of Belgium, Ringlaan 3, B-1180, Brussels (Belgium)
4. Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)
5. Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG-USP), Universidade de São Paulo, Cidade Universitária, Rua do Matão 1226, São Paulo, SP, 05508-090 (Brazil)
6. Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Manchester, M13 9PL (United Kingdom)
7. Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, E-28049, Madrid (Spain)
8. Leiden Observatory, Universiteit Leiden, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
9. Chester F. Carlson Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Dr., Rochester, NY, 14623 (United States)
10. N. Copernicus Astronomical Centre Rabianska 8, 87–100 Torun (Poland)

We perform a comprehensive analysis of the planetary nebula (PN) NGC 6781 to investigate the physical conditions of each of its ionized, atomic, and molecular gas and dust components and the object’s evolution, based on panchromatic observational data ranging from UV to radio. Empirical nebular elemental abundances, compared with theoretical predictions via nucleosynthesis models of asymptotic giant branch (AGB) stars, indicate that the progenitor is a solar-metallicity, 2.25--3.0 M{sub ⊙} initial-mass star. We derive the best-fit distance of 0.46 kpc by fitting the stellar luminosity (as a function of the distance and effective temperature of the central star) with the adopted post-AGB evolutionary tracks. Our excitation energy diagram analysis indicates high-excitation temperatures in the photodissociation region (PDR) beyond the ionized part of the nebula, suggesting extra heating by shock interactions between the slow AGB wind and the fast PN wind. Through iterative fitting using the Cloudy code with empirically derived constraints, we find the best-fit dusty photoionization model of the object that would inclusively reproduce all of the adopted panchromatic observational data. The estimated total gas mass (0.41 M{sub ⊙}) corresponds to the mass ejected during the last AGB thermal pulse event predicted for a 2.5 M{sub ⊙} initial-mass star. A significant fraction of the total mass (about 70%) is found to exist in the PDR, demonstrating the critical importance of the PDR in PNe that are generally recognized as the hallmark of ionized/H{sup +} regions.

• OSTI ID: 22872564
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 231; ISSN 0067-0049; ISSN APJSA2
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC DUST
DISSOCIATION
EXCITATION
GIANT STARS
HEATING
HYDROGEN IONS 1 PLUS
LUMINOSITY
MASS
METALLICITY
NUCLEOSYNTHESIS
PHOTOIONIZATION
PHOTOLYSIS
PLANETARY NEBULAE
ULTRAVIOLET RADIATION