A. Peimbert,1 M. Peimbert,1 G. Delgado-Inglada,1 J. García-Rojas,2 and M. Peña1
1 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264. México, 04510 D. F., México (gdelgado, antonio, peimbert, miriam@astro.unam.mx).
2 Instituto de Astrofísica de Canarias (IAC), 38200, La Laguna, Tenerife, Spain; Universidad de La Laguna, Dept. Astrofísica, 38206, La Laguna, Tenerife, Spain (jogarcia@iac.es).
Received June 30 2014.
Accepted August 5 2014.
RESUMEN
A partir de observaciones de alta calidad del multiplete V1 de OII estudiamos la densidad y la temperatura de una muestra de nebulosas planetarias. Encontramos que, en general, las densidades que obtenemos a partir de las líneas de O II son similares a las densidades obtenidas a partir de líneas prohibidas. Esto implica que no hay evidencia de condensaciones de alta densidad y baja temperatura para la mayoría de los objetos de nuestra muestra. Las presiones electrónicas encontradas en las zonas calientes son semejantes o ligeramente mayores que las de las zonas frías, sugiriendo la presencia de ondas de choque. Las temperaturas promedio y los valores de t2 obtenidos a partir de líneas de H, He y O son similares y consistentes con un medio químicamente homogéneo. Estos resultados sugieren que las abundancias obtenidas a partir de las líneas de recombinación son las representativas de estos objetos.
ABSTRACT
Based on high quality observations of multiplet V1 of OII and the NLTE atomic computations for OII we study the density and temperature of a sample of PNe. We find that, in general, the densities derived from recombination lines of O II are similar to the densities derived from forbidden lines. This implies that the signature for oxygen rich clumps of high density and low temperature is absent in most of the objects of our sample. Electron pressures derived from the hotter zones are similar or slightly larger than those derived from the colder zones, suggesting the presence of shock waves. The average temperatures and t2 values derived from H, He and O lines are similar and consistent with chemical homogeneity. These results suggest that the abundances of these objects are the ones derived from recombination lines.
Key Words: ISM: abundances — planetary nebulae: general.
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]]> ACKNOWLEDGMENTS
We thank the referee for a critical reading of the manuscript and several useful suggestions. G Delgado-Inglada gratefully acknowledges a DGAPA postdoctoral grant from the Universidad Nacional Autónoma de México (UNAM). J. García-Rojas acknowledges funding by the Spanish Ministry of Economy and Competitiveness (MINECO) under the grant AYA2011-22614 and Severo Ochoa SEV-2011-0187. A. Peimbert, M. Peimbert, and M. Peña are grateful for the finantial support provided by CONACyT (grant 129753).
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