Extrapolation of Galactic Dust Emission at 100 Microns to Cosmic Microwave Background Radiation Frequencies Using FIRAS
D. P. Finkbeiner, M. Davis, D. J. Schlegel;
ApJ, 1999, 524, 867
ABSTRACT:We present predicted full-sky maps of submillimeter and microwave emission from the diffuse interstellar dust in the Galaxy.
These maps are
extrapolated from the 100 μm emission and 100/240 μm flux ratio maps that
Schlegel, Finkbeiner, & Davis generated from IRAS and COBE/DIRBE
data.
Results are presented for a number of physically plausible emissivity
models.
The correlation of COBE/FIRAS data with the simple Schlegel, Finkbeiner,
& Davis (ν^2 emissivity power law) extrapolation is much tighter
than with other common dust templates such as H I column density or 100 μm
emission.
Despite the apparent success of the Schlegel, Finkbeiner, & Davis
extrapolation, the assumed ν^2 emissivity is inconsistent with the FIRAS data
below 800 GHz.
Indeed, no power-law emissivity function fits the FIRAS data
from 200 to 2100 GHz.
In this paper we provide a formalism for a
multicomponent model for the dust emission.
A two-component model with a mixture of
``silicate'' and ``carbon-dominated'' grains (motivated by Pollack et al.)
provides a fit to an accuracy of ~15% to all the FIRAS data over the entire
high-latitude sky.
Small systematic differences are found between the atomic and
molecular phases of the ISM.
COBE/DMR has observed microwave emission that is
correlated with thermal dust emission.
However, this emission is higher than our
model predicts by factors of 1.2, 2.4, and 20 at 90, 53, and 31 GHz,
respectively.
This provides evidence that another emission mechanism dominates dust
emission at frequencies below ~60 GHz.
Our predictions for the thermal
(vibrational) emission from Galactic dust at ν<3000 GHz are available for
general use.
These full-sky predictions can be made at the DIRBE resolution of
40' or at the higher resolution of 6&farcm;1 from the Schlegel,
Finkbeiner, & Davis DIRBE-corrected IRAS maps.
KEYWORDS: ism: dust, extinction, infrared: ism: continuum, submillimeter
PERSOKEY:dust, fir, iras, submillimeter, ,
CODE: finkbeiner99