Biases in the kinematic parallaxes of galactic planetary nebulae
It has recently been noted that the kinematic parallaxes of planetary nebulae(PNe) may be significantly in error. The pattern velocities of the shells, whichdetermine the lateral expansion of the outows, are likely to differ from line-ofsightvelocities determined through visual spectroscopy. It is u...
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| Formato: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2005 |
| País: | México |
| Recursos: | Universidad de Guadalajara |
| Repositorio: | Redalyc-UDG |
| OAI Identifier: | oai:redalyc.org:57141212 |
| Acesso em linha: | https://www.redalyc.org/articulo.oa?id=57141212 |
| Access Level: | acceso abierto |
| Palavra-chave: | Física, Astronomía y Matemáticas ISM: JETS AND OUTFLOWS PLANETARY NEBULAE: GENERAL |
| Resumo: | It has recently been noted that the kinematic parallaxes of planetary nebulae(PNe) may be significantly in error. The pattern velocities of the shells, whichdetermine the lateral expansion of the outows, are likely to differ from line-ofsightvelocities determined through visual spectroscopy. It is usually assumed thatthe mean distances to large ensembles of PNe should be reasonably secure, however.Given that sources are randomly oriented with respect to the line-of-sight, thenindividual distance biases should wash-out in the mean. We point out that this isunlikely to be the case where sources possess non-spherical structures, however. Ifone measures lateral expansion velocities V? along the minimum axes of the sources,then distances will (in the mean) tend to be somewhat too large. Alternatively, ifone consistently determines V? along the largest axes of the outows, then valuesof <D> will tend to be low. Although the size of error is difficult to assess, it mayapproach of order D=D 10%. |
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