First detection of the warm ionised medium dust emission. Implication for the cosmic far-infrared background
G. Lagache, A. Abergel, F. Boulanger, F. X. Désert, J. L. Puget;
AaA, 1999, 344, 322
ABSTRACT:We present a new analysis of the far-IR emission at high Galactic latitude based on COBE and HI data.
A decomposition of the Far-IR emission over
the H_I, H(+) and H_2 Galactic gas components and the Cosmic Far InfraRed
Background (CFIRB) is described.
For the first time the far-IR emission of dust
associated with the Warm Ionised Medium (WIM) is evidenced.
This component
determined on about 25% of the sky is detected at a 10sigma level in the [200, 350]
microns band.
The best representation of the WIM dust spectrum is obtained for
a temperature of 29.1 K and an emissivity law tau /N_H(+=) 3.8 +/- 0.8
10(-26) (lambda /250 microns )(-1) cm(2) .
With a spectral index equal to 2, the
emissivity law becomes tau /N_H(+=) 1.0 +/- 0.2 10(-25) (lambda /250 microns )(-2)
cm(2) , with a temperature of 20 K, which is significantly higher than the
temperature of dust associated with HI gas.
The variation in the dust spectrum from
the HI to the WIM component can be explained by only changing the upper
cutoff of the Big Grain size distribution from 0.1 microns to 30 nm.
The
detection of IR emission of dust in the WIM significantly decreases the intensity
of the CFIRB, especially around 200 microns which corresponds to the peak
of energy.
KEYWORDS: ism: dust, extinction, ism: general, cosmology: cosmic microwave background, cosmology: observations, infrared: ism: continuum, submillimeter
PERSOKEY:dust, h+, dirbe, h_i, h2, ,
CODE: lagache99