Galaxies and quasars are thought to provide the bulk of the photons responsible for ionizing the hydrogen in the intergalactic medium (IGM). We use a large set of hydrodynamical simulations, combined with measurements of the Lyα opacity of the IGM taken from the literature, to obtain robust estimates of the photoionization rate per hydrogen atom at z = 5 and 6. We find the photoionization rate ...

Primordial magnetic fields present between the eras of neutrino decoupling and of positron-electron annihilation can lead to the emission of neutrinoanti neutrino pairs or axions by electrons in excited Landau levels, thereby changing the electron energy spectrum. The rate is calculated and shown to not affect significantly the standard Big Bang picture.

We have observed a core in the northern streamer of the IC5146 cloud using the MPIfR 19-channel Bolometer system on the IRAM 30m telescope at a wavelength of 1.2 mm. We smoothed our observations to the same angular resolution (30) as a new map of the NIR extinction of this cloud (Lada, Alves, and Lada 1998) and in this way obtained direct measurements of the ratio of millimeter emissivity to du...

A blackbody is any object that absorbs all the electromagnetic radiation incident upon it, and that emits spectral radiation that is solely dependent on the object’s kinetic temperature. Real-world objects seldom exhibit this behavior, and are termed spectral greybodies. A spectral greybody does not absorb all the incident energy, it differentially absorbs this energy as a function of wavelengt...

A hand-held, battery-powered Fourier transform infrared spectroradiometer weighing 12.5 kg has been developed for the field measurement of spectral radiance from the Earth's surface and atmosphere in the 3-5-µm and 8-14-µm atmospheric windows, with a 6-cm(-1) spectral resolution. Other versions of this instrument measure spectral radiance between 0.4 and 20 µm, using different optical materials...

The efficiency of the application of high-emissivity coatings on the furnace walls in steam cracking technology can only be evaluated on the asis of a description of radiative heat transfer distinguishing between the frequency bands. To this end, a non-grey gas radiation model based on he exponential wide band model (EWBM) has been developed and applied in the context of three-dimensional CFD s...

For a foam-covered sea surface, it is difficult to retrieve sea surface salinity (SSS) with L-band brightness temperature (1.4 GHz) because of the effect of a foam layer with wind speeds stronger than 7 m/s, especially at low sea surface temperature (SST). With foam-controlled experiments, emissivities of a foam-covered water surface at low SST (−1.4 °C to 1.7 °C) are measured for varying SSS, ...