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Radiative transfer

About: Radiative transfer is a research topic. Over the lifetime, 43287 publications have been published within this topic receiving 1176539 citations.


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TL;DR: In this paper, a statistical narrow-band (SNB) model for H2O, CO2, CH4 and CO, and correlated-k (CK) parameters for H 2O and CO2 are generated from line by line calculations and recently improved spectroscopic databases in wide temperature and spectral ranges.

189 citations

Journal ArticleDOI
TL;DR: In this article, a cosmological reionization simulation with box size of 100Mpc/h on a side and a Monte Carlo Lyman-alpha (Lya) radiative transfer code was used to model Lyman Alpha Emitters (LAEs) at z~5.7.
Abstract: We combine a cosmological reionization simulation with box size of 100Mpc/h on a side and a Monte Carlo Lyman-alpha (Lya) radiative transfer code to model Lyman Alpha Emitters (LAEs) at z~5.7. The model introduces Lya radiative transfer as the single factor for transforming the intrinsic Lya emission properties into the observed ones. Spatial diffusion of Lya photons from radiative transfer results in extended Lya emission and only the central part with high surface brightness can be observed. Because of radiative transfer, the appearance of LAEs depends on density and velocity structures in circumgalactic and intergalactic media as well as the viewing angle, which leads to a broad distribution of apparent (observed) Lya luminosity for a given intrinsic Lya luminosity. Radiative transfer also causes frequency diffusion of Lya photons. The resultant Lya line is asymmetric with a red tail. The peak of the Lya line shifts towards longer wavelength and the shift is anti-correlated with the apparent to intrinsic Lya luminosity ratio. The simple radiative transfer model provides a new framework for studying LAEs. It is able to explain an array of observed properties of z~5.7 LAEs in Ouchi et al. (2008), producing Lya spectra, morphology, and apparent Lya luminosity function (LF) similar to those seen in observation. The broad distribution of apparent Lya luminosity at fixed UV luminosity provides a natural explanation for the observed UV LF, especially the turnover towards the low luminosity end. The model also reproduces the observed distribution of Lya equivalent width (EW) and explains the deficit of UV bright, high EW sources. Because of the broad distribution of the apparent to intrinsic Lya luminosity ratio, the model predicts effective duty cycles and Lya escape fractions for LAEs.

189 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed a pragmatic approximation in order to enable multi-dimensional simulations with basic spectral radiative transfer when the computational resources are not sufficient to solve the complete Boltzmann transport equation.
Abstract: Astrophysical observations originate from matter that interacts with radiation or transported particles. We develop a pragmatic approximation in order to enable multi-dimensional simulations with basic spectral radiative transfer when the computational resources are not sufficient to solve the complete Boltzmann transport equation. The distribution function of the transported particles is decomposed into trapped and streaming particle components. Their separate evolution equations are coupled by a source term that converts trapped particles into streaming particles. We determine this source term by requiring the correct diffusion limit. For a smooth transition to the free streaming regime, this 'diffusion source' is limited by the matter emissivity. The resulting streaming particle emission rates are integrated over space to obtain the streaming particle flux. A geometric estimate of the flux factor is used to convert the particle flux to the streaming particle density. The efficiency of the scheme results from the freedom to use different approximations for each particle component. In supernovae, reactions with trapped particles on fast time scales establish equilibria that reduce the number of primitive variables required to evolve the trapped particle component. On the other hand, a stationary-state approximation facilitates the treatment of the streaming particle component. Different approximations may apply in applications to stellar atmospheres, star formation, or cosmological radiative transfer. We compare the isotropic diffusion source approximation with Boltzmann neutrino transport of electron flavour neutrinos in spherically symmetric supernova models and find good agreement. An extension of the scheme to the multi-dimensional case is also discussed.

189 citations

Journal ArticleDOI
TL;DR: In this article, the correlated-k and scaled-k distribution methods for radiative heat transfer in molecular gases are developed based on precise mathematical principles, for both narrow band and full spectrum models.
Abstract: The correlated-k and scaled-k distribution methods for radiative heat transfer in molecular gases are developed based on precise mathematical principles, for both narrow band and full spectrum models. Their differences and commonalities are high-lighted and discussed. Applications to narrow spectral bands of nonhomogeneous gases show both methods to be about equally accurate. For full-spectrum calculations, on the other hand, the scaled-k distribution consistently outperforms the correlated-k model.

189 citations

Journal ArticleDOI
TL;DR: In this paper, the decay time spectra, wavelengths, and intensities of fast (ns) radiative recombination in five direct, wide-bandgap semiconductors: CuI, HgI2, PbI2 and n-doped ZnO:Ga and CdS:In.
Abstract: We present temperature-dependent pulsed X-ray data on the decay time spectra, wavelengths, and intensities of fast (ns) radiative recombination in five direct, wide-bandgap semiconductors: CuI, HgI2, PbI2, and n-doped ZnO:Ga and CdS:In. At 12 K the luminosity of powder samples is 0.30, 1.6, 0.40, 2.0, and 0.15, respectively, relative to that of BGO powder at room temperature. Increasing the temperature of CuI to 346 K decreases the luminosity by a factor of 300 while decreasing the fwhm of the decay time spectra from 0.20 to 0.11 ns. Increasing the temperature of HgI2 to 102 K decreases the luminosity by a factor of 53 while decreasing the fwhm from 1.6 to 0.5 ns. Increasing the temperature of PbI2 to 165 K decreases the luminosity by a factor of 27 while decreasing the fwhm from 0.52 to 0.15 ns. Increasing the temperature of ZnO:Ga to 365 K decreases the luminosity by a factor of 33 while decreasing the fwhm from 0.41 to 0.21 ns. Increasing the temperature of CdS:In to 295 K decreases the luminosity by a factor of 30 while decreasing the fwhm from 0.20 to 0.17 ns. All emission wavelengths are near the band edge. The luminosities decrease much faster than the radiative lifetimes, therefore, the reduction in luminosity is not primarily due to thermal quenching of the excited states, but mostly due to thermally activated trapping of charge carriers on nonradiative recombination centers. Since the radiative and nonradiative processes occur on different centers, increasing the ratio of radiative to nonradiative centers could result in a class of inorganic scintillators whose decay time and radiative efficiency would approach fundamental limits (i.e.

189 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,706
20223,291
20211,335
20201,335
20191,429
20181,409