The far-infrared continuum spectrum of the MilkyWay explained by a dust and gas model

E-ISSN： 1286-4854|34|1|69-74

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.34, Iss.1, 2010-03, pp. : 69-74

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

The far-infrared continuum spectra observed in the FIRAS-COBEmission are explained by a one-component dust source in the Galaxyand a cold excess due to radiation of molecular hydrogen gas in the outer Galaxy. The dust model is based on an empiricallytested temperature-dependent mass absorption coefficient and areasonable dust density distribution close to the galacticplane. The temperature of the dust along the line of sight isdetermined by a fit curve. The gas source is conceivable as a small part of cold molecular hydrogen and helium gas in the outer Galaxywhich is only observable in a small temperature interval at 11 K and at corresponding (equilibrium )condensation densities of about $\rm 4.5\cdot 10^{18} \; cm ^{-3}$. It is assumed that the high densitiesoccur in very small and short-living inhomogeneities of the fractal-structured gas due to self-gravitation, turbulence and startingcondensation in the elementary fragments,i.e. the gas is at a stage close to star formation.Preliminary tests show that the gas sources are very likely correlated with the well-known HI sources in the outer Galaxy.The gas sources contribute to the spectra still at latitudes up to |b| lt; 25–30 degrees, while the instrument noise is larger at higher latitudes.