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Authordc.contributor.authorCasassus Montero, Simón es_CL
Authordc.contributor.authorNyman, L. A. es_CL
Authordc.contributor.authorDickinson, C. 
Authordc.contributor.authorPearson, T. J. es_CL
Admission datedc.date.accessioned2013-01-14T20:27:48Z
Available datedc.date.available2013-01-14T20:27:48Z
Publication datedc.date.issued2007-12-21
Cita de ítemdc.identifier.citationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Volume: 382 Issue: 4 Pages: 1607-1622 Published: DEC 21 2007es_CL
Identifierdc.identifier.issn0035-8711
Identifierdc.identifier.otherDOI: 10.1111/j.1365-2966.2007.12366.x
Identifierdc.identifier.urihttps://repositorio.uchile.cl/handle/2250/125738
General notedc.descriptionArtículo de publicación ISIes_CL
Abstractdc.description.abstractWe report a centimetre-wave (cm-wave, 5-31 GHz) excess over free-free emission in planetary nebulae (PNe). Accurate 31- and 250-GHz measurements show that the 31-GHz flux densities in our sample are systematically higher than the level of optically thin free-free continuum extrapolated from 250-GHz. The 31-GHz excess is observed, within one standard deviation, in all 18 PNe with reliable 31- and 250-GHz data, and is significant in nine PNe. The only exception is the peculiar object M2-9, whose radio spectrum is that of an optically thick stellar wind. On average the fraction of non-free-free emission represents 51 per cent of the total flux density at 31 GHz, with a scatter of 11 per cent. The average 31-250 GHz spectral index of our sample is <alpha(250)(31)> = -0.43 +/- 0.03 (in flux density, with a scatter of 0.14). The 31-250 GHz drop is reminiscent of the anomalous foreground observed in the diffuse interstellar medium (ISM) by cosmic microwave background (CMB) anisotropy experiments. The 5-31 GHz spectral indices are consistent with both flat spectra and spinning dust emissivities, given the 10 per cent calibration uncertainty of the comparison 5-GHz data. However, a detailed study of the objects with the largest cm-excess, including the low-frequency data available in the literature, shows that present spinning dust models alone cannot explain the cm-wave excess in PNe. Although we have no definitive interpretation of our data, the least implausible explanation involves a synchrotron component absorbed by a cold nebular screen. We give flux densities for 37 objects at 31 GHz, and for 26 objects at 250 GHz.es_CL
Lenguagedc.language.isoenes_CL
Publisherdc.publisherWILEY-BLACKWELLes_CL
Keywordsdc.subjectradiation mechanisms : generales_CL
Títulodc.titleA centimetre-wave excess over free–free emission in planetary nebulaees_CL
Document typedc.typeArtículo de revista


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