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Dust-correlated centimetre-wave radiation from the M78 reflection nebula

Castellanos, Pablo; Casassus, Simon; Dickinson, Clive; Vidal, Matías; Paladini, Roberta; Cleary, Kieran; Davies, Rodney D.; Davis, Richard J.; White, Glenn J. and Taylor, Angela (2011). Dust-correlated centimetre-wave radiation from the M78 reflection nebula. Monthly Notices of the Royal Astronomical Society, 411(2) pp. 1137–1150.

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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 interstellar medium. In this work, we focus on one particular dark cloud, the bright reflection nebula M78. The main goal of this work is to investigate the cm-wave continuum emission in a prominent molecular cloud, nearby and with complementary observational data. We acquired Cosmic Background Imager (CBI) visibility data of M78 at 31 GHz with an angular resolution of ~5.8 arcmin, and CBI2 data at an angular resolution of ~4.2 arcmin. A morphological analysis was undertaken to search for possible correlations with templates that trace different emission mechanisms. Using data from Wilkinson Microwave Anisotropy Probe and the Rhodes/HartRAO 2326-MHz survey, we constructed the spectral energy distribution (SED) of M78 in a 45-arcmin circular aperture. We used results from the literature to constrain the physical conditions and the stellar content. The 5–31 GHz spectral index in flux density ( α= 1.89 ± 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 (CBI resolutions). However, a free–free background dominates at cm-wavelengths on large scales (~1°). We correct for this uniform background by differencing against a set of reference fields. The differenced SED of M78 shows excess emission at 10–70 GHz over free–free and a modified blackbody, at 3.4σ. The excess is matched by the spinning dust model from Draine & Lazarian.

Item Type: Journal Item
Copyright Holders: 2010 Royal Astronomical Society, 2010 Universidad de Chile
ISSN: 1365-2966
Project Funding Details:
Funded Project NameProject IDFunding Body
Not SetREA-236176Marie Curie International
Not Set1100221FONDECYT
Not Set15010003Chilean Center for Astrophysics (FONDAP)
Advanced FellowshipNot SetSTFC (Science & Technology Facilities Council)
Not SetNot SetERC under the FP7
Not SetNot SetStrategic Alliance for the Implementation of New Technologies
Not Set09-ADP09-0059NASA/ADP ROSES-2009
Keywords: radiation mechanisms; ISM: clouds; dust: extinction; infrared: ISM; radio continuum: ISM
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Related URLs:
Item ID: 25339
Depositing User: Tracy Bartlett
Date Deposited: 13 Dec 2010 17:05
Last Modified: 07 Dec 2018 17:12
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