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Article: Observations and three-dimensional photoionization modelling of the wolf-Rayet planetary nebula NGC 1501

TitleObservations and three-dimensional photoionization modelling of the wolf-Rayet planetary nebula NGC 1501
Authors
KeywordsAtomic Data
Ism: Abundances
Planetary Nebulae: Individual: Ngc 1501
Stars: Wolf-Rayet
Issue Date2004
PublisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNR
Citation
Monthly Notices Of The Royal Astronomical Society, 2004, v. 354 n. 2, p. 558-574 How to Cite?
AbstractDeep optical spectra of the high-excitation planetary nebula NGC 1501 and its W04 central star are presented. A recombination line abundance analysis of the emission-line spectrum of the central star yields He C: O mass fractions of 0.36:0.48:0.16, similar to those of PG 1159 stars. A detailed empirical analysis of the nebular collisionally excited line (CEL) and optical recombination line (ORL) spectrums are presented, together with fully three-dimensional photoionization modelling of the nebula. We found very large ORL-CEL abundance discrepancy factors (ADFs) for O 2+ (32) and Ne 2+ (33). The mean value of∼5100 K for the T e derived from Her recombination lines ratios is 6000 K, lower than the value of 11 100 K implied by the [O III] line ratio. This result indicates the existence of a second, low-temperature nebular component, which could account for the observed ORL emission. Electron temperature fluctuations (t 2) cannot account for the high ADFs found from our optical spectra of this nebula. A three-dimensional photoionization model of NGC 1501 was constructed using the photoionization code MOCASSIN, based on our new spectroscopic data and using the three-dimensional electron density distribution determined from long-slit echellograms of the nebula by Ragazzoni et al. The central star ionizing radiation field is approximated by a model atmosphere, calculated using the Tübingen non-local thermodynamic equilibrium model atmosphere package, for abundances typical of the W04 nucleus of NGC 1501 and PG 1159 stars. The nebular emission-line spectrum was best reproduced using a central star model with an effective temperature of T eff = 110 kK and a luminosity of L* = 5000L ⊙ The initial models showed higher degrees of ionization of heavy elements than indicated by observations. We investigated the importance of the missing low-temperature dielectronic recombination rates for third-row elements and have estimated upper limits to their rate coefficients. Our single-phase, three-dimensional photoionization model heavily underpredicts the optical recombination line emission. We conclude that the presence of a hydrogen-deficient, metal-rich component is necessary to explain the observed ORL spectrum of this object. The existence of such knots could also provide a softening of the radiation field, via the removal of ionizing photons by absorption in the knots, thereby helping to alleviate the overionization of the heavy elements in our models.
Persistent Identifierhttp://hdl.handle.net/10722/175164
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorErcolano, Ben_US
dc.contributor.authorWesson, Ren_US
dc.contributor.authorZhang, Yen_US
dc.contributor.authorBarlow, MJen_US
dc.contributor.authorDe Marco, Oen_US
dc.contributor.authorRauch, Ten_US
dc.contributor.authorLiu, XWen_US
dc.date.accessioned2012-11-26T08:49:31Z-
dc.date.available2012-11-26T08:49:31Z-
dc.date.issued2004en_US
dc.identifier.citationMonthly Notices Of The Royal Astronomical Society, 2004, v. 354 n. 2, p. 558-574en_US
dc.identifier.issn0035-8711en_US
dc.identifier.urihttp://hdl.handle.net/10722/175164-
dc.description.abstractDeep optical spectra of the high-excitation planetary nebula NGC 1501 and its W04 central star are presented. A recombination line abundance analysis of the emission-line spectrum of the central star yields He C: O mass fractions of 0.36:0.48:0.16, similar to those of PG 1159 stars. A detailed empirical analysis of the nebular collisionally excited line (CEL) and optical recombination line (ORL) spectrums are presented, together with fully three-dimensional photoionization modelling of the nebula. We found very large ORL-CEL abundance discrepancy factors (ADFs) for O 2+ (32) and Ne 2+ (33). The mean value of∼5100 K for the T e derived from Her recombination lines ratios is 6000 K, lower than the value of 11 100 K implied by the [O III] line ratio. This result indicates the existence of a second, low-temperature nebular component, which could account for the observed ORL emission. Electron temperature fluctuations (t 2) cannot account for the high ADFs found from our optical spectra of this nebula. A three-dimensional photoionization model of NGC 1501 was constructed using the photoionization code MOCASSIN, based on our new spectroscopic data and using the three-dimensional electron density distribution determined from long-slit echellograms of the nebula by Ragazzoni et al. The central star ionizing radiation field is approximated by a model atmosphere, calculated using the Tübingen non-local thermodynamic equilibrium model atmosphere package, for abundances typical of the W04 nucleus of NGC 1501 and PG 1159 stars. The nebular emission-line spectrum was best reproduced using a central star model with an effective temperature of T eff = 110 kK and a luminosity of L* = 5000L ⊙ The initial models showed higher degrees of ionization of heavy elements than indicated by observations. We investigated the importance of the missing low-temperature dielectronic recombination rates for third-row elements and have estimated upper limits to their rate coefficients. Our single-phase, three-dimensional photoionization model heavily underpredicts the optical recombination line emission. We conclude that the presence of a hydrogen-deficient, metal-rich component is necessary to explain the observed ORL spectrum of this object. The existence of such knots could also provide a softening of the radiation field, via the removal of ionizing photons by absorption in the knots, thereby helping to alleviate the overionization of the heavy elements in our models.en_US
dc.languageengen_US
dc.publisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNRen_US
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_US
dc.subjectAtomic Dataen_US
dc.subjectIsm: Abundancesen_US
dc.subjectPlanetary Nebulae: Individual: Ngc 1501en_US
dc.subjectStars: Wolf-Rayeten_US
dc.titleObservations and three-dimensional photoionization modelling of the wolf-Rayet planetary nebula NGC 1501en_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.doi10.1111/j.1365-2966.2004.08218.xen_US
dc.identifier.scopuseid_2-s2.0-7044260870en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-7044260870&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume354en_US
dc.identifier.issue2en_US
dc.identifier.spage558en_US
dc.identifier.epage574en_US
dc.identifier.isiWOS:000224466000027-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridErcolano, B=7801345025en_US
dc.identifier.scopusauthoridWesson, R=7003586236en_US
dc.identifier.scopusauthoridZhang, Y=23768446500en_US
dc.identifier.scopusauthoridBarlow, MJ=18041819500en_US
dc.identifier.scopusauthoridDe Marco, O=7003988805en_US
dc.identifier.scopusauthoridRauch, T=7005242319en_US
dc.identifier.scopusauthoridLiu, XW=7409287288en_US

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