Dust-correlated centimetre-wave radiation from the M 78 reflection nebula
| Autor: | Castellanos, Pablo, Casassus, Simon, Dickinson, Clive, Vidal, Matias, Paladini, Roberta, Cleary, Kieran, Davies, Rodney D., Davis, Richard J., White, Glenn J., Taylor, Angela |
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| Rok vydání: | 2010 |
| Předmět: | |
| Zdroj: | MNRAS, 441, 1137 (2011) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1111/j.1365-2966.2010.17743.x |
| Popis: | An anomalous radio continuum component at cm-wavelengths has been observed in various sources, including dark clouds. This continuum component represents a new property of the ISM. In this work we focus on one particular dark cloud, the bright reflection nebula M 78. The main goal of this work is to invetigate cm-wave continuum emission in a prominent molecular cloud, nearby and with complementary observational data. We acquired Cosmic Background Imager (CBI) visibility data of M 78 at 31 GHz with an angular resolution of $\sim 5.8\arcmin$ and CBI2 data at an angular resolution of $\sim 4.2\arcmin$. A morphological analysis was undertaken to search for possible correlations with templates that trace different emission mechanisms. Using data from WMAP and the Rhodes/HartRAO 2326 MHz survey we constructed the spectral energy distribution (SED) of M 78 in a $45\arcmin$ circular aperture. We used results from the literature to constrain the physical conditions and the stellar content. The 5 GHz -- 31 GHz spectral index in flux density ($\alpha = 1.89\pm 0.15$) is significantly different from optically thin free-free values. We also find closer morphological agreement with IR dust tracers than with free-free sources. Dust-correlated cm-wave emission that is not due to free-free is significant at small scales ($\sim 8\arcmin$). However, a free-free background dominates at cm-wavelengths on large scales ($\sim 1$ deg). We correct for this uniform background by differencing against a set of reference fields. The differenced SED of M 78 shows excess emission at 10-70 GHz over free-free and a modified blackbody, at $3.4\sigma$. The excess is matched by the spinning dust model from Draine and Lazarian (1998). Comment: 15 pages, 12 figures |
| Databáze: | arXiv |
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