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Article: Integrated spectrum of the planetary nebula NGC 7027

TitleIntegrated spectrum of the planetary nebula NGC 7027
Authors
KeywordsIsm: Abundances
Ism: Planetary Nebulae: Individual: Ngc 7027
Line: Identification
Issue Date2005
PublisherE D P Sciences. The Journal's web site is located at http://www.aanda.org
Citation
Astronomy And Astrophysics, 2005, v. 442 n. 1, p. 249-262 How to Cite?
AbstractWe present deep optical spectra of the archetypal young planetary nebula (PN) NGC7027, covering a wavelength range from 3310 to 9160 Å. The observations were carried out by uniformly scanning a long slit across the entire nebular surface, thus yielding average optical spectra for the whole nebula. A total of 937 emission features are detected. The extensive line list presented here should prove valuable for future spectroscopic analyses of emission line nebulae. The optical data, together with the archival IUE and ISO spectra, are used to probe the temperature and density structures and to determine the elemental abundances from lines produced by different excitation mechanisms. Electron temperatures have been derived from the hydrogen recombination Balmer jump (BJ), from ratios of He I optical recombination lines (ORLs) and from a variety of diagnostic ratios of collisionally excited lines (CELs). Electron densities have been determined from the intensities of high-order H I Balmer lines and of He II Pfund lines, as well as from a host of CEL diagnostic ratios. CEL and ORL diagnostics are found to yield compatible results. Adopting respectively electron temperatures of T e = 12 600 and 15 500 K for ions with ionization potentials lower or higher than 50 eV and a constant density of N e = 47 000 cm -3, elemental abundances have been determined from a large number of CELs and ORLs. The C 2+/H +, N 2+/H +, O 2+/H + and Ne 2+/H + ionic abundance ratios derived from ORLs are found to be only slightly higher than the corresponding CEL values. We conclude that whatever mechanism is causing the BJ/CEL temperature discrepanies and the ORL/CEL abundance discrepancies that have been observed in many PNe, it has an insignificant effect on this bright young compact PN. The properties of the central star are also discussed. Based on the integrated spectrum and using the energy-balance method, we have derived an effective temperature of 219 000 K for the ionizing star. Finally, we report the first detection in the spectrum of this bright young PN of Raman-scattered O VI features at 6830 and 7088 Å, pointing to the existence of abundant neutral hydrogen around the ionized regions. © ESO 2005.
Persistent Identifierhttp://hdl.handle.net/10722/174974
ISSN
2014 Impact Factor: 4.378
2015 SCImago Journal Rankings: 2.446
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhang, Yen_US
dc.contributor.authorLiu, XWen_US
dc.contributor.authorLuo, SGen_US
dc.contributor.authorPéquignot, Den_US
dc.contributor.authorBarlow, MJen_US
dc.date.accessioned2012-11-26T08:48:27Z-
dc.date.available2012-11-26T08:48:27Z-
dc.date.issued2005en_US
dc.identifier.citationAstronomy And Astrophysics, 2005, v. 442 n. 1, p. 249-262en_US
dc.identifier.issn0004-6361en_US
dc.identifier.urihttp://hdl.handle.net/10722/174974-
dc.description.abstractWe present deep optical spectra of the archetypal young planetary nebula (PN) NGC7027, covering a wavelength range from 3310 to 9160 Å. The observations were carried out by uniformly scanning a long slit across the entire nebular surface, thus yielding average optical spectra for the whole nebula. A total of 937 emission features are detected. The extensive line list presented here should prove valuable for future spectroscopic analyses of emission line nebulae. The optical data, together with the archival IUE and ISO spectra, are used to probe the temperature and density structures and to determine the elemental abundances from lines produced by different excitation mechanisms. Electron temperatures have been derived from the hydrogen recombination Balmer jump (BJ), from ratios of He I optical recombination lines (ORLs) and from a variety of diagnostic ratios of collisionally excited lines (CELs). Electron densities have been determined from the intensities of high-order H I Balmer lines and of He II Pfund lines, as well as from a host of CEL diagnostic ratios. CEL and ORL diagnostics are found to yield compatible results. Adopting respectively electron temperatures of T e = 12 600 and 15 500 K for ions with ionization potentials lower or higher than 50 eV and a constant density of N e = 47 000 cm -3, elemental abundances have been determined from a large number of CELs and ORLs. The C 2+/H +, N 2+/H +, O 2+/H + and Ne 2+/H + ionic abundance ratios derived from ORLs are found to be only slightly higher than the corresponding CEL values. We conclude that whatever mechanism is causing the BJ/CEL temperature discrepanies and the ORL/CEL abundance discrepancies that have been observed in many PNe, it has an insignificant effect on this bright young compact PN. The properties of the central star are also discussed. Based on the integrated spectrum and using the energy-balance method, we have derived an effective temperature of 219 000 K for the ionizing star. Finally, we report the first detection in the spectrum of this bright young PN of Raman-scattered O VI features at 6830 and 7088 Å, pointing to the existence of abundant neutral hydrogen around the ionized regions. © ESO 2005.en_US
dc.languageengen_US
dc.publisherE D P Sciences. The Journal's web site is located at http://www.aanda.orgen_US
dc.relation.ispartofAstronomy and Astrophysicsen_US
dc.subjectIsm: Abundancesen_US
dc.subjectIsm: Planetary Nebulae: Individual: Ngc 7027en_US
dc.subjectLine: Identificationen_US
dc.titleIntegrated spectrum of the planetary nebula NGC 7027en_US
dc.typeArticleen_US
dc.identifier.emailZhang, Y: zhangy96@hku.hken_US
dc.identifier.authorityZhang, Y=rp00841en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1051/0004-6361:20052869en_US
dc.identifier.scopuseid_2-s2.0-27144487795en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-27144487795&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume442en_US
dc.identifier.issue1en_US
dc.identifier.spage249en_US
dc.identifier.epage262en_US
dc.identifier.isiWOS:000232230600022-
dc.publisher.placeFranceen_US
dc.identifier.scopusauthoridZhang, Y=23768446500en_US
dc.identifier.scopusauthoridLiu, XW=7409287288en_US
dc.identifier.scopusauthoridLuo, SG=7401986047en_US
dc.identifier.scopusauthoridPéquignot, D=6603066408en_US
dc.identifier.scopusauthoridBarlow, MJ=18041819500en_US

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