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An anomalous radio continuum component at cm-wavelengths has been observed invarious sources, including dark clouds. This continuum component represents a newproperty of the ISM. In this work we focus on one particular dark cloud, the brightreection nebula M 78. The main goal of this work is to investigate the cm-wavecontinuum emission in a prominent molecular cloud, nearby and with complementaryobservational data. We acquired Cosmic Background Imager CBI visibility data ofM 78 at 31 GHz with an angular resolution of 5:80, and CBI2 data at an angularresolution of 4:20. A morphological analysis was undertaken to search for possiblecorrelations with templates that trace di erent emission mechanisms. Using data fromWMAP and the Rhodes-HartRAO 2326 MHz survey we constructed the spectral en-ergy distribution SED of M 78 in a 450 circular aperture. We used results from theliterature to constrain the physical conditions and the stellar content. The 5 GHz {31 GHz spectral index in ux density = 1:89 0:15 is signi cantly di erent fromoptically thin-free-free values. We also nd closer morphological agreement with IRdust tracers than with free-free sources. Dust-correlated cm-wave emission that is notdue to free-free is signi cant at small scales CBI resolutions. However, a free-freebackground dominates at cm-wavelengths on large scales 1 deg. We correct forthis uniform background by di erencing against a set of reference elds. The di er-enced SED of M 78 shows excess emission at 10-70 GHz over free-free and a modi edblackbody, at 3.4 . The excess is matched by the spinning dust model from Draineand Lazarian 1998.Nota general

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Author: Castellanos, Pablo; - Dickinson, Clive; - Vidal, Matías; - Paladini, Roberta; - Cleary, Kieran; - Davies, Rodney D.; - Davis, Ri

Source: http://repositorio.uchile.cl/



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