Omphile Rabyang | Searcharxiv

arXiv2025

Investigating the H i mass-size relation using the Simba cosmological simulations

Observational studies have established a remarkably tight power-law relationship between the H I masses and sizes of late-type galaxies, known as the H I mass-size relation. This relation has been shown to persist across various models of a galaxy's H I surface density profile. Using the Simba cosmological simulations, we investigate the robustness of this relation under different feedback prescriptions, including cases where specific feedback mechanisms are absent. While the global properties of galaxies are significantly affected by changes in feedback, the H I mass-size relation remains intact. Moreover, its parameters consistently align with the best available empirical measurements. We analyze the H I mass distributions of galaxies and demonstrate that, regardless of the feedback scenario, galaxies within a given H I mass bin exhibit outer H I radial profiles well approximated by an exponential function. Furthermore, the exponential decline rate remains remarkably similar across different physical prescriptions. We attribute the persistence of the H I mass-size relation to this inherent self-similarity in the H I mass distributions.

astro-ph.GA↗

arXiv2023

The atomic-to-molecular hydrogen transition in the TNG50 simulation: Using realistic UV fields to create spatially resolved HI 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, postprocessing 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 HI 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 HI maps are less concentrated than their WHISP counterparts (median $ΔC\approx0.3$), due in part to central HI deficits related to the ejective character of supermassive black hole feedback in TNG. In terms of the HI column density distribution function, we find discrepancies between WHISP and IllustrisTNG that depend on the total HI abundance in these datasets as well as the postprocessing method. To fully exploit the synergy between cosmological simulations and upcoming deep HI/H2 data, we advocate the use of accurate methods to estimate the UV radiation field and to generate mock maps.

astro-ph.GA↗