arXiv subjects

Martin Glatzle

Publications and source records attributed to Martin Glatzle.

6 recordsLinked to original sources

arXiv2022

Thermodynamic modeling for numerical simulations based on the generalized cubic equation of state

We further elaborate on the generalized formulation for cubic equation of state proposed by Cismondi and Mollerup [Fluid Phase Equilib. 232 (2005)]. With this formulation all well-known cubic equations of state can be described with a certain pair of values, which allows for a generic implementation of different equations of state. Based on this generalized formulation, we derive a complete thermodynamic model for computational fluid dynamics (CFD) simulations by providing the resulting correlations for all required thermodynamic properties. For the transport properties, we employ the Chung correlations. Our generic implementation includes the often used equations of state Soave-Redlich-Kwong and Peng-Robinson and the Redlich-Kwong-Peng-Robinson (RKPR) equation of state. The first two assume a universal compressibility factor and are therefore only suitable for fluids with a matching critical compressibility. The Redlich-Kwong-Peng-Robinson overcomes this limitation by considering the equation of state parameter as function of the critical compressibility. We compare the resulting thermodynamic modeling for the three equations of state for selected fluids with each other and CoolProp reference data. As supplementary material to this paper, we provide a Python tool called real gas thermodynamic python library (realtpl). This tool can be used to evaluate and compare the results for a wide range of different fluids. Additionally, we also provide the implementation of the generalized form in OpenFOAM.

physics.flu-dyn↗

arXiv2022

Ionizing photon production and escape fractions during cosmic reionization in the TNG50 simulation

In this work we investigate the dependence of the escape fraction of ionizing photons, $f_{\rm esc}$, on various galaxy and host halo properties during the epoch of reionization. We post-process the TNG50 magneto-hydrodynamical simulation from the IllustrisTNG project using the 3D multi-frequency radiative transfer code CRASH. Our work covers the stellar mass range $10^6 \lesssim M_\star/{\rm M_\odot} \lesssim 10^8$ at redshifts $6 < z < 10$. Adopting an unresolved, cloud-scale escape fraction parameter of unity, the halo escape fraction $f_{\rm esc}$ increases with mass from $\sim 0.3$ at $M_\star = 10^6$M$_\odot$ to $\sim 0.6$ at $M_\star = 10^{7.5}$M$_\odot$, after which we find hints of a turnover and decreasing escape fractions for even more massive galaxies. However, we demonstrate a strong and non-linear dependence of $f_{\rm esc}$ on the adopted sub-grid escape fraction. In addition, $f_{\rm esc}$ has significant scatter at fixed mass, driven by diversity in the ionizing photon rate together with a complex relationship between (stellar) source positions and the underling density distribution. The global emissivity is consistent with observations for reasonable cloud-scale absorption values, and halos with a stellar mass $\lesssim 10^{7.5}$M$_\odot$ contribute the majority of ionizing photons at all redshifts. Incorporating dust reduces $f_{\rm esc}$ by a few percent at $M_\star \lesssim 10^{6.5}$M$_\odot$, and up to 10\% for larger halos. Our multi-frequency approach shows that $f_{\rm esc}$ depends on photon energy, and is reduced substantially at $E>54.4$eV versus lower energies. This suggests that the impact of high energy photons from binary stars is reduced when accounting for an energy dependent escape fraction.

astro-ph.GA↗

arXiv2021

Radiative transfer of ionizing radiation through gas and dust: grain charging in star forming regions

The presence of charged dust grains is known to have a profound impact on the physical evolution of the multiphase interstellar medium (ISM). Despite its importance, this process is still poorly explored in numerical simulations due to its complex physics and the tight dependence on the environment. Here we introduce a novel implementation of grain charging in the cosmological radiative transfer code CRASH. We first benchmark the code predictions on a series of idealized dusty HII regions created by a single star, in order to assess the impact of grain properties on the resulting spatial distribution of charges. Second, we perform a realistic radiative transfer simulation of a star forming region extracted from a dusty galaxy evolving in the Epoch of Reionization. We find that $\sim 13$ % of the total dust mass gets negatively charged, mainly silicate and graphite grains of radius micron. A complex spatial distribution of grain charges is also found, primarily depending on the exposure to stellar radiation and strongly varying along different lines of sight, as a result of radiative transfer effects. We finally assess the impact of grain properties (both chemical composition and size) on the resulting charge distribution. The new implementation described here will open up a wide range of possible studies investigating the physical evolution of the dusty ISM, nowadays accessible to observations of high and low redshift galaxies.

astro-ph.GA↗

arXiv2021

The physical origins and dominant emission mechanisms of Lyman-alpha halos: results from the TNG50 simulation in comparison to MUSE observations

Extended Lyman-alpha emission is now commonly detected around high redshift galaxies through stacking and even on individual basis. Despite recent observational advances, the physical origin of these Lyman-alpha halos (LAHs), as well as their relationships to galaxies, quasars, circumgalactic gas, and other environmental factors remains unclear. We present results from our new Lyman-alpha full radiative transfer code voroILTIS which runs directly on the unstructured Voronoi tessellation of cosmological hydrodynamical simulations. We make use of the TNG50 simulation and simulate LAHs from redshift $z=2$ to $z=5$, focusing on star-forming galaxies with $8.0 < \log_{10}{(M_\star/\rm{M}_\odot)} < 10.5$. While TNG50 does not directly follow ionizing radiation, it includes an on-the-fly treatment for active galactic nuclei and ultraviolet background radiation with self-shielding, which are important processes impacting the cooling and ionization of the gas. Based on this model, we present the predictions for the stacked radial surface brightness profiles of Ly$α$ as a function of galaxy mass and redshift. Comparison with data from the MUSE UDF at $z>3$ reveals a promising level of agreement. We measure the correlations of LAH size and central brightness with galaxy properties, finding that at the masses of $8.5 \leq \log_{10} \left(M_\star/\rm{M}_\odot\right) \leq 9.5$, physical LAH sizes roughly double from $z=2$ to $z=5$. Finally, we decompose the profiles into contributions from diffuse emission and scattered photons from star-forming regions. In our simulations, we find rescattered photons from star-forming regions to be the major source in observed LAHs. Unexpectedly, we find that the flattening of LAH profiles at large radii becomes dominated by photons originating from other nearby halos rather than diffuse emission itself.

astro-ph.GA↗

arXiv2021

Optical reconstruction of dust in the region of SNR RX J1713.7-3946 from astrometric data

The origin of the radiation observed in the region of the supernova remnant RX J1713.7-3946, one of the brightest TeV emitters, has been debated since its discovery. The existence of atomic and molecular clouds in this object supports the idea that part of the GeV gamma rays in this region originate from proton-proton collisions. However, the observed column density of protons derived from gas observations cannot explain the whole emission. Yet there could be a fraction of protons contained in fainter structures that have note been detected so far. Here we search for faint objects in the line of sight of RX J1713.7-3946 using the principle of light extinction and the ESA/Gaia DR2 astrometric and photometric data. We reveal and locate with precision a number of dust clouds and note that only one appears to be in the vicinity of RX J1713.7-3946. We estimate the embedded mass to $M_{dust} = (7.0 \pm 0.6) \times 10^3 \, M_{\odot}$ which might be big enough to contain the missing protons. Finally, using the fact that the supernova remnant is expected to be located in a dusty environment and that there appears to be only one such structure in the vicinity of RX J1713.7-3946, we set a very precise constrain to the supernova remnant distance, at ($1.12 \pm 0.01$) kpc.

astro-ph.HE↗

arXiv2018

Radiative transfer of ionizing radiation through gas and dust: stellar source case

We present a new dust extension to the Monte Carlo radiative transfer code crash, which enables it to simulate the propagation of ionizing radiation through mixtures of gas and dust. The new code is applied to study the impact of dust absorption on idealized galactic H II regions and on small scale reionization. We find that H II regions are reduced in size by the presence of dust, while their inner temperature and ionization structure remain largely unaffected. In the small scale reionization simulation, dust hardens ionization fronts and delays the overlap of ionized bubbles. This effect is found to depend only weakly on the assumed abundance of dust in underdense regions.

astro-ph.GA↗