High-resolution synthetic UV-submm images for Milky Way-mass simulated galaxies from the ARTEMIS project

We present redshift-zero synthetic dust-aware observations for the 45 Milky Way-mass simulated galaxies of the ARTEMIS project, calculated with the SKIRT radiative transfer code. The post-processing procedure includes components for star-forming regions, stellar sources, and diffuse dust. We produce and publicly release realistic high-resolution images for 50 commonly-used broadband filters from ultraviolet to sub-millimetre wavelengths and for 18 different viewing angles. We compare the simulated ARTEMIS galaxies to observed galaxies in the DustPedia database with similar stellar mass and star formation rate, and to synthetic observations of the simulated galaxies of the Auriga project produced in previous work using a similar post-processing technique. In all cases, global galaxy properties are derived using SED fitting. We find that, similar to Auriga, the post-processed ARTEMIS galaxies generally reproduce the observed scaling relations for global fluxes and physical properties, although dust extinction at FUV/UV wavelengths is underestimated and representative dust temperatures are lower than observed. At a resolved scale, we compare multi-wavelength non-parametric morphological properties of selected disc galaxies across the data sets. We find that the ARTEMIS galaxies largely reproduce the observed morphological trends as a function of wavelength, although they appear to be more clumpy and less symmetrical than observed. We note that the ARTEMIS and Auriga galaxies occupy adjacent regions in the specific star formation versus stellar mass plane, so that the synthetic observation data sets supplement each other.Comment: Accepted for publication by MNRA

The atomic-to-molecular hydrogen transition in the TNG50 simulation:Using realistic UV fields to create spatially resolved H i maps

Cold gas in galaxies provides a crucial test to evaluate the realism of cosmological hydrodynamical simulations. To extract the atomic and molecular hydrogen properties of the simulated galaxy population, post-processing methods taking the local UV field into account are required. We improve upon previous studies by calculating realistic UV fields with the dust radiative transfer code SKIRT to model the atomic-to-molecular transition in TNG50, the highest-resolution run of the IllustrisTNG suite. Comparing integrated quantities such as the H i mass function, we study to what detail the UV field needs to be modelled in order to calculate realistic cold gas properties. We then evaluate new, spatially resolved comparisons for cold gas in galaxies by exploring synthetic maps of atomic hydrogen at redshift zero and compare them to 21-cm observations of local galaxies from the WHISP survey. In terms of non-parametric morphologies, we find that TNG50 H i maps are less concentrated than their WHISP counterparts (median ΔC ≈ 0.3), due in part to central H i deficits related to the ejective character of supermassive black hole feedback in TNG. In terms of the H i column density distribution function, we find discrepancies between WHISP and IllustrisTNG that depend on the total H i abundance in these data sets as well as the post-processing method. To fully exploit the synergy between cosmological simulations and upcoming deep H i/H2 data, we advocate the use of accurate methods to estimate the UV radiation field and to generate mock maps.</p

CAPTURING EXHAUST CO2 GAS USING MOLTEN CARBONATE FUEL CELLS

Carbon dioxide is considered as one of the major contenders when the question of greenhouse effect arises. So for any industry or power plant it is of utmost importance to follow certain increasingly stringent environment protection rules and laws. So it is significant to keep eye on any possible methods to reduce carbon dioxide emissions in an efficient way. This paper reviews the available literature so as to try to provide an insight of the possibility of using Molten Carbonate Fuel Cells (MCFCs) as the carbon capturing and segregating devices and the various factors that affect the performance of MCFCs during the process of CO2 capture

A new analytical scattering phase function for interstellar dust

Context. Properly modelling scattering by interstellar dust grains requires a good characterisation of the scattering phase function. The Henyey-Greenstein phase function has become the standard for describing anisotropic scattering by dust grains, but it is a poor representation of the real scattering phase function outside the optical range. Aims: We investigate alternatives for the Henyey-Greenstein phase function that would allow the scattering properties of dust grains to be described. Our goal is to find a balance between realism and complexity: the scattering phase function should be flexible enough to provide an accurate fit to the scattering properties of dust grains over a wide wavelength range, and it should be simple enough to be easy to handle, especially in the context of radiative transfer calculations. Methods: We fit various analytical phase functions to the scattering phase function corresponding to the BARE-GR-S model, one of the most popular and commonly adopted models for interstellar dust. We weigh the accuracy of the fit against the number of free parameters in the analytical phase functions. Results: We confirm that the Henyey-Greenstein phase functions poorly describe scattering by dust grains, particularly at ultraviolet (UV) wavelengths, with relative differences of up to 50%. The Draine phase function alleviates this problem at near-infrared (NIR) wavelengths, but not in the UV. The two-term Reynolds-McCormick phase function, recently advocated in the context of light scattering in nanoscale materials and aquatic media, describes the BARE-GR-S data very well, but its five free parameters are degenerate. We propose a simpler phase function, the two-term ultraspherical-2 (TTU2) phase function, that also provides an excellent fit to the BARE-GR-S phase function over the entire UV-NIR wavelength range. This new phase function is characterised by three free parameters with a simple physical interpretation. We demonstrate that the TTU2 phase function is easily integrated in both the spherical harmonics and the Monte Carlo radiative transfer approaches, without a significant overhead or increased complexity. Conclusions: The new TTU2 phase function provides an ideal balance between being simple enough to be easily adopted and realistic enough to accurately describe scattering by dust grains. We advocate its application in astrophysical applications, in particular in dust radiative transfer calculations

Reduction of dust radial drift by turbulence in protoplanetary disks

International audienceContext. Dust particles in protoplanetary disks rotate at velocities exceeding those of the surrounding gas due to a lack of pressure support. Consequently, they experience a headwind from the gas that drives them toward the central star. Radial drift occurs on timescales much shorter than those inferred from disk observations or those required for dust to aggregate and form planets. Additionally, turbulence is often assumed to amplify the radial drift of dust in planet-forming disks when modeled through an effective viscous transport. However, the local interactions between turbulent eddies and particles are known to be significantly more intricate than in a viscous fluid.Aims. Our objective is to elucidate and characterize the dynamic effects of Keplerian turbulence on the mean radial and azimuthal velocities of dust particles.Methods. We employed 2D shearing-box incompressible simulations of the gas, which is maintained in a developed turbulent state while rotating at a sub-Keplerian speed. Dust is modeled as Lagrangian particles set at a Keplerian velocity, therefore experiencing a radial force toward the star through drag.Results. Turbulent eddies are found to reduce the radial drift, while simultaneously enhancing the azimuthal velocities of small particles. This dynamic behavior arises from the modification of dust trajectories due to turbulent eddies

Effects of spatial discretization in Ly α line radiation transfer simulations

We describe the addition of Lyα resonant line transfer to our dust continuum radiation transfer code SKIRT, verifying our implementation with published results for spherical problems and using some self-designed three-dimensional setups. We specifically test spatial discretization through various grid types, including hierarchical octree grids and unstructured Voronoi tessellations. We then use a radiation transfer postprocessing model for one of the spiral galaxies produced by the Auriga cosmological zoom simulations to investigate the effect of spatial discretization on the synthetic observations. We find that the calculated Lyα line profiles exhibit an extraordinarily strong dependence on the type and resolution of the spatial grid, rendering the results untrustworthy at best. We attribute this effect to the large gradients in the hydrogen density distribution over small distances, which remain significantly underresolved in the input model. We therefore argue that further research is needed to determine the required spatial resolution of a hydrodynamical simulation snapshot to enable meaningful Lyα line transfer postprocessing

UV to submillimetre luminosity functions of TNG50 galaxies

We apply the radiative transfer (RT) code SKIRT on a sample of ∼14000 low-redshift (z ≤ 0.1) galaxies extracted from the TNG50 simulation to enable an apples-to-apples comparison with observations. The RT procedure is calibrated via comparison of a subsample of TNG50 galaxies with the DustPedia observational sample: we compare several luminosity and colour scaling relations and spectral energy distributions in different specific SFR bins. We consistently derive galaxy luminosity functions for the TNG50 simulation in 14 broad-band filters from UV to submillimetre wavelengths and investigate the effects of the aperture, orientation, radiative transfer recipe, and numerical resolution. We find that, while our TNG50+RT fiducial model agrees well with the observed luminosity functions at the knee (±0.04 dex typical agreement), the TNG50 + RT luminosity functions evaluated within 5R1/2 are generally higher than observed at both the faint and bright ends, by 0.004 (total IR)-0.27 (UKIDSS H) dex and 0.12 (SPIRE250)-0.8 (GALEX FUV) dex, respectively. A change in the aperture does affect the bright end of the luminosity function, easily by up to 1 dex depending on the choice. However, we also find that the galaxy luminosity functions of a worse-resolution run of TNG50 (TNG50-2, with eight times worse mass resolution than TNG50, similar to TNG100) are in better quantitative agreement with observational constraints. Finally, we publicly release the photometry for the TNG50 sample in 53 broad-bands from FUV to submillimetre, in three orientations and four apertures, as well as galaxy spectral energy distributions

High-resolution synthetic UV–submm images for simulated Milky Way-type galaxies from the Auriga project

We present redshift-zero synthetic observational data considering dust attenuation and dust emission for the 30 galaxies of the Auriga project, calculated with the skirt radiative transfer code. The post-processing procedure includes components for star-forming regions, stellar sources, and diffuse dust taking into account stochastic heating of dust grains. This allows us to obtain realistic high-resolution broad-band images and fluxes from ultraviolet (UV) to submillimetre (submm) wavelengths. For the diffuse dust component, we consider two mechanisms for assigning dust to gas cells in the simulation. In one case, only the densest or the coldest gas cells are allowed to have dust, while in the other case this condition is relaxed to allow a larger number of dust-containing cells. The latter approach yields galaxies with a larger radial dust extent and an enhanced dust presence in the interspiral regions. At a global scale, we compare Auriga galaxies with observations by deriving dust scaling relations using spectral energy distribution fitting. At a resolved scale, we make a multiwavelength morphological comparison with nine well-resolved spiral galaxies from the DustPedia observational data base. We find that for both dust assignment methods, although the Auriga galaxies show a good overall agreement with observational dust properties, they exhibit a slightly higher specific dust mass. The multiwavelength morphological analysis reveals a good agreement between the Auriga and the observed galaxies in the optical wavelengths. In the mid- and far-infrared wavelengths, Auriga galaxies appear smaller and more centrally concentrated in comparison to their observed counterparts. We publicly release the multi-observer images and fluxes in 50 commonly used broad-band filters

Spatially resolved mock observations of stellar kinematics : full radiative transfer treatment of simulated galaxies

We present a framework to build realistic mock spectroscopic observations for state-of-the-art hydrodynamical simulations, using high spectral resolution stellar population models and full radiative transfer treatment with SKIRT. As a first application we generate stellar continuum mock observations for the Auriga cosmological zoom simulations emulating integral-field observations from the SAMI Galaxy survey. We perform spectral fitting on our synthetic cubes and compute the resulting rotation velocity (Vrot) and velocity dispersion within 1Re (σe) for a sub-set of the Auriga sample. We find that the kinematics produced by Auriga are in good agreement with the observations from the SAMI Galaxy survey after taking into account the effects of dust and the systematics produced by the observation limitations. We also explore the effects of seeing convolution, inclination, and attenuation on the line-of-sight velocity distribution. For highly inclined galaxies, these effects can lead to an artificial decrease in the measured V/σ by nearly a factor two (after inclination correction). We also demonstrate the utility of our method for high-redshift galaxies by emulating spatially resolved continuum spectra from the LEGA-C survey and, looking forward, E-ELT HARMONI. Our framework represents a crucial link between the ground truth for stellar populations and kinematics in simulations and the observed stellar continuum observations at low and high redshift

High-resolution synthetic UV–submm images for simulated Milky Way-type galaxies from the Auriga project

We present redshift-zero synthetic observational data considering dust attenuation and dust emission for the 30 galaxies of the Auriga project, calculated with the skirt radiative transfer code. The post-processing procedure includes components for star-forming regions, stellar sources, and diffuse dust taking into account stochastic heating of dust grains. This allows us to obtain realistic high-resolution broad-band images and fluxes from ultraviolet (UV) to submillimetre (submm) wavelengths. For the diffuse dust component, we consider two mechanisms for assigning dust to gas cells in the simulation. In one case, only the densest or the coldest gas cells are allowed to have dust, while in the other case this condition is relaxed to allow a larger number of dust-containing cells. The latter approach yields galaxies with a larger radial dust extent and an enhanced dust presence in the interspiral regions. At a global scale, we compare Auriga galaxies with observations by deriving dust scaling relations using spectral energy distribution fitting. At a resolved scale, we make a multiwavelength morphological comparison with nine well-resolved spiral galaxies from the DustPedia observational data base. We find that for both dust assignment methods, although the Auriga galaxies show a good overall agreement with observational dust properties, they exhibit a slightly higher specific dust mass. The multiwavelength morphological analysis reveals a good agreement between the Auriga and the observed galaxies in the optical wavelengths. In the mid- and far-infrared wavelengths, Auriga galaxies appear smaller and more centrally concentrated in comparison to their observed counterparts. We publicly release the multi-observer images and fluxes in 50 commonly used broad-band filters