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The Sejong Suite: Cosmological Hydrodynamical Simulations with Massive Neutrinos, Dark Radiation, and Warm Dark Matter

We present the Sejong Suite, an extensive collection of state-of-the-art high-resolution cosmological hydrodynamical simulations spanning a variety of cosmological and astrophysical parameters, primarily developed for modeling the Lyman-Alpha (LyA) forest. The suite is organized into three main categories (Grid Suite, Supporting Suite, and Systematics Suite), addressing different science targets. Adopting a particle-based implementation, we follow the evolution of gas, dark matter (cold and warm), massive neutrinos, and dark radiation, and consider several combinations of box sizes and number of particles. With additional enhancing techniques, we are able to reach an equivalent resolution up to 3x3328^3=110 billion particles in a (100 Mpc/h)^3 box size, ideal for current and future surveys (e.g., eBOSS, DESI). Noticeably, for the first time, we simulate extended mixed scenarios describing the combined effects of warm dark matter, neutrinos, and dark radiation, modeled consistently by taking into account the neutrino mass splitting. In addition to providing multicomponent snapshots from z=5.0 to z=2.0 in intervals of dz=0.2 for all of the models considered, we produced over 288 million LyA skewers in the same z-range and extended parameter space. The skewers are well suited for LyA forest science studies, for mapping the high-$z$ cosmic web and the matter-to-flux relation and bias, and for quantifying the critical role of baryons at small scales. We also present a first analysis of the suite focused on the matter and flux statistics, and show that we are able to accurately reproduce the 1D flux power spectrum down to scales k=0.06 [s/km] as mapped by recent high-resolution quasar data, as well as the thermal history of the intergalactic medium. The simulations and products described here will be progressively made available.