Artículos de revistas
Dust-correlated centimetre-wave radiation from the M78 reflection nebula
Fecha
2011-02Registro en:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Volume: 411 Issue: 2 Pages: 1137-1150 Published: FEB 2011
0035-8711
DOI: 10.1111/j.1365-2966.2010.17743.x
Autor
Castellanos, Pablo
Casassus Montero, Simón
Dickinson, Clive
Vidal, Matías
Paladini, Roberta
Cleary, Kieran
Davies, Rodney D.
Davis, Richard J.
White, Glenn J.
Taylor, Angela C.
Institución
Resumen
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
re
ection nebula M 78. 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
M 78 at 31 GHz with an angular resolution of 5:80, and CBI2 data at an angular
resolution of 4:20. A morphological analysis was undertaken to search for possible
correlations with templates that trace di erent emission mechanisms. Using data from
WMAP 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 the
literature 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 from
optically thin-free-free values. We also nd 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 signi cant at small scales (CBI resolutions). However, a free-free
background dominates at cm-wavelengths on large scales ( 1 deg). We correct for
this 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 ed
blackbody, at 3.4 . The excess is matched by the spinning dust model from Draine
& Lazarian (1998).