sígame v3: Gas Fragmentation in Postprocessing of Cosmological Simulations for More Accurate Infrared Line Emission Modeling

We present an update to the framework called Simulator of Galaxy Millimeter/submillimeter Emission (SÍGAME). SÍGAME derives line emission in the far-infrared (FIR) for galaxies in particle-based cosmological hydrodynamics simulations by applying radiative transfer and physics recipes via a postprocessing step after completion of the simulation. In this version, a new technique is developed to model higher gas densities by parameterizing the probability distribution function (PDF) of the gas density in higher-resolution simulations run with the pseudoLagrangian, Voronoi mesh code AREPO. The parameterized PDFs are used as a look-up table, and reach higher densities than in previous work. SÍGAME v3 is tested on redshift z = 0 galaxies drawn from the SIMBA cosmological simulation for eight FIR emission lines tracing vastly different phases of the interstellar medium. This version of SÍGAME includes dust radiative transfer with SKIRT and high-resolution photoionization models with CLOUDY, the latter sampled according to the density PDF of the AREPO simulations to augment the densities in the cosmological simulation. The quartile distributions of the predicted line luminosities overlap with the observed range for nearby galaxies of similar star formation rate (SFR) for all but two emission lines: [O I]63 and CO(3–2), which are overestimated by median factors of 1.3 and 1.0 dex, respectively, compared to the observed line–SFR relation of mixed-type galaxies. We attribute the remaining disagreement with observations to the lack of precise attenuation of the interstellar light on sub-grid scales (200 pc) and differences in sample selection

FORMALISM FOR NUMERICAL RELATIVISTIC SIMULATIONS OF CHARGED BLACK HOLES NEAR EXTREMAL LIMIT: PUNCTURE GAUGE TECHNIQUE

The Weak Cosmic Censorship Conjecture states that a spacetime singularity is always hidden inside of a black hole’s event horizon. However, this conjecture is violated for charged black holes that exceed the extremal limit, |Q|/M = 1. To theoretically test the credibility of the weak cosmic censorship conjecture, we can utilize a simulation of a charged black hole that is near the extremal limit and try to exceed the extremal limit by using various tests that could impart more charge on this near-extremal black hole such that its charge by mass ratio increases. In this thesis, we develop the formalism to simulate charged black holes that are near the extremal limit using the puncture gauge technique. We transform the Reissner-Nordstr¨om metric to a new coordinate system containing a radial coordinate that is modified from a quasi-isotropic radial coordinate to avoid difficulties that arise in the simulation. Using this, we derive the initial conditions for the simulation of a nonrotating, charged black hole and verify it using the Hamiltonian and the momentum constraints