Related papers: On the accuracy of common moment-based radiative t…
The "Reduced Speed of Light" (RSL) approximation is commonly used to speed up radiative transfer calculations in cosmological simulations. However, it has been shown previously that the RSL approximation leads to photon non-conservation in…
We consider imaging of fast moving small objects in space, such as low earth orbit satellites. The imaging system consists of ground based, asynchronous sources of radiation and several passive receivers above the dense atmosphere. We use…
An iterative method is derived for image reconstruction. Among other attributes, this method allows constraints unrelated to the radiation measurements to be incorporated into the reconstructed image. A comparison is made with the widely…
We employ the recently developed multi-photon R-matrix method for molecular above-threshold photoionization to obtain second-order ionization amplitudes that govern the interference in RABITT experiments. This allows us to extract RABITT…
Aims: To incorporate background subtraction into the Bayesian Blocks algorithm so that transient events can be timed accurately and precisely even in the presence of a substantial, rapidly variable, background. Methods: We developed several…
In a semi-numerical model of reionization, the evolution of ionization fraction is simulated approximately by the ionizing photon to baryon ratio criterion. In this paper we incorporate a semi-analytical model of galaxy formation based on…
We describe and test an updated version of radiation-hydrodynamics (RHD) in the RAMSES code, that includes three new features: i) radiation pressure on gas, ii) accurate treatment of radiation diffusion in an unresolved optically thick…
Modifications of photoionization arising from resonant electron-electron correlations between neighbouring atoms in an atomic sample are studied. The sample contains atomic species A and B, with the ionization potential of A being smaller…
Attosecond ionization time-delays at photoelectron energies above typically 10 eV are usually interpreted using the so called asymptotic approximation as a sum of the atomic or molecular delays with a universal laser-induced contribution.…
Most astrophysical plasmas entail a balance between ionization and recombination. We present new results from the powerful R-matrix method which yields in an ab initio manner: (I) self-consistent photoionization and recombination cross…
Achieving efficient and accurate simulation of the radiative transfer has long been a research challenge. Here we introduce the general synthetic iterative scheme as an easy-to-implement approach to address this issue. First, a macroscopic…
When modelling the ionisation of gas in the intergalactic medium after reionisation, it is standard practice to assume a uniform radiation background. This assumption is not always appropriate; models with radiative transfer show that…
To elucidate the permeation of cosmic ultraviolet (UV) background radiation into a pregalactic cloud and subsequent ionization, the frequency-dependent radiative transfer equation is solved, coupled with the ionization process. A spherical…
Observations of the HI 21cm transition line promises to be an important probe into the cosmic dark ages and epoch of reionization. One of the challenges for the detection of this signal is the accuracy of the foreground source removal. This…
Observations of the end stages of reionization indicate that at $z\approx 5-6$, the ionizing background is not uniform and the mean free path (MFP) changes drastically. As MFP is closely related to the distribution of Lyman Limit Systems…
This paper presents a new technique for developing reduced-order models (ROMs) for nonlinear radiative transfer problems in high-energy density physics. The proper orthogonal decomposition (POD) of photon intensities is applied to obtain…
We show that perturbative techniques inspired by effective field theory (EFT) can be used to "paint on" the 21~cm field during reionization using only the underlying linear density field. This procedure is accurate to within O(10%) on large…
The observed scatter in intergalactic Lyman-$\alpha$ opacity at $z \lesssim 6$ requires large-scale fluctuations in the neutral fraction of the intergalactic medium (IGM) after the expected end of reionization. Post-reionization models that…
Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. An identical eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring…
We present simulations of the 21-cm signal during the epoch of reionization. We focus on properly modeling the absorption regime in the presence of inhomogeneous Wouthuysen-Field effect and X-ray heating. We ran radiative transfer…