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dc.contributor.authorKimura, Rafael Kobatapt_BR
dc.contributor.authorGruenwald, Ruth B.pt_BR
dc.contributor.authorAleman, Isabel Regina Guerrapt_BR
dc.date.accessioned2014-08-05T02:07:37Zpt_BR
dc.date.issued2012pt_BR
dc.identifier.issn0004-6361pt_BR
dc.identifier.urihttp://hdl.handle.net/10183/99092pt_BR
dc.description.abstractContext. Detections of molecular lines, mainly from H₂ and CO, reveal molecular material in planetary nebulae. Observations of a variety of molecules suggest that the molecular composition in these objects differs from that found in interstellar clouds or in circumstellar envelopes. The success of the models, which are mostly devoted to explain molecular densities in specific planetary nebulae, is still partial however. Aims. The present study aims at identifying the influence of stellar and nebular properties on the molecular composition of planetary nebulae by means of chemical models. A comparison of theoretical results with those derived from the observations may provide clues to the conditions that favor the presence of a particular molecule. Methods. A self-consistent photoionization numerical code was adapted to simulate cold molecular regions beyond the ionized zone. The code was used to obtain a grid of models and the resulting column densities are compared with those inferred from observations. Results. Our models show that the inclusion of an incident flux of X-rays is required to explain the molecular composition derived for planetary nebulae. We also obtain a more accurate relation for the N(CO)/N(H₂) ratio in these objects. Molecular masses obtained by previous works in the literature were then recalculated, showing that these masses can be underestimated by up to three orders of magnitude. We conclude that the problem of the missing mass in planetary nebulae can be solved by a more accurate calculation of the molecular mass.en
dc.format.mimetypeapplication/pdf
dc.language.isoengpt_BR
dc.relation.ispartofAstronomy and astrophysics. Les Ulis. Vol. 541 (May 2012), A112, 11 p.pt_BR
dc.rightsOpen Accessen
dc.subjectAstrochemistryen
dc.subjectMatéria circumestelarpt_BR
dc.subjectISM: moleculessen
dc.subjectAstroquímicapt_BR
dc.subjectMoleculas interestelarespt_BR
dc.subjectPlanetary nebulae: generalen
dc.subjectMatéria circumestelarpt_BR
dc.subjectNuvens moleculares interestelarespt_BR
dc.subjectNebulosas planetariaspt_BR
dc.subjectFotoionizacaopt_BR
dc.titleMolecular chemistry and the missing mass problem in planetary nebulaept_BR
dc.typeArtigo de periódicopt_BR
dc.identifier.nrb000900161pt_BR
dc.type.originEstrangeiropt_BR


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