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Abstract Traditional star formation subgrid models implemented in cosmological galaxy formation simulations, such as that of V. Springel & L. Hernquist (hereafter SH03), employ adjustable parameters to satisfy constraints measured in the local Universe. In recent years, however, theory and spatially resolved simulations of the turbulent, multiphase, star-forming interstellar medium (ISM) have begun to produce new first-principles models, which when fully developed can replace traditional subgrid prescriptions. This approach has advantages of being physically motivated and predictive rather than empirically tuned, and allowing for varying environmental conditions rather than being tied to local-Universe conditions. As a prototype of this new approach, by combining calibrations from the TIGRESS numerical framework with the pressure-regulated feedback-modulated (PRFM) theory, simple formulae can be obtained for both the gas depletion time and an effective equation of state. Considering galaxies in TNG50, we compare the “native” simulation outputs with postprocessed predictions from PRFM. At TNG50 resolution, the total midplane pressure is nearly equal to the total ISM weight, indicating that galaxies in TNG50 are close to satisfying vertical equilibrium. The measured gas scale height is also close to theoretical equilibrium predictions. The slopes of the effective equations of states are similar, but with effective velocity dispersion normalization from SH03 slightly larger than that from current TIGRESS simulations. Because of this and the decrease in PRFM feedback yield at high pressure, the PRFM model predicts shorter gas depletion times than the SH03 model at high densities and redshift. Our results represent a first step toward implementing new, numerically calibrated subgrid algorithms in cosmological galaxy formation simulations. 

ABSTRACT The tension between the diverging density profiles in Lambda cold dark matter simulations and the constant-density inner regions of observed galaxies is a long-standing challenge known as the ‘core–cusp’ problem. We demonstrate that the SMUGGLE galaxy formation model implemented in the arepo moving mesh code forms constant-density cores in idealized dwarf galaxies of M⋆ ≈ 8 × 107 Msun with initially cuspy dark matter (DM) haloes of M200 ≈ 1010 Msun. Identical initial conditions run with an effective equation of state interstellar medium model preserve cuspiness. Literature on the subject has pointed to the low density threshold for star formation, ρth, in such effective models as an obstacle to baryon-induced core formation. Using a SMUGGLE run with equal ρth, we demonstrate that core formation can proceed at low density thresholds, indicating that ρth is insufficient on its own to determine whether a galaxy develops a core. We reaffirm that the ability to resolve a multiphase interstellar medium at sufficiently high densities is a more reliable indicator of core formation than any individual model parameter. In SMUGGLE, core formation is accompanied by large degrees of non-circular motion, with gas rotational velocity profiles that consistently fall below the circular velocity $$v_\text{circ} = \sqrt{GM/R}$$ out to ∼2 kpc. Asymmetric drift corrections help recover the average underlying DM potential for some of our less efficient feedback runs, but time-variations in the instantaneous azimuthal gas velocity component are substantial, highlighting the need for careful modelling in the inner regions of dwarfs to infer the true distribution of DM. 

ABSTRACT We present a suite of 16 high-resolution hydrodynamic simulations of an isolated dwarf galaxy (gaseous and stellar disc plus a stellar bulge) within an initially cuspy dark matter (DM) halo, including self-interactions between the DM particles; as well as stochastic star formation and subsequent supernova feedback (SNF), implemented using the stellar feedback model SMUGGLE. The simulations start from identical initial conditions, and we regulate the strength of DM self-interactions and SNF by systematically varying the self-interacting DM (SIDM) momentum transfer cross-section and the gas density threshold for star formation. The DM halo forms a constant density core of similar size and shape for several combinations of those two parameters. Haloes with cores that are formed due to SIDM (adiabatic cusp-core transformation) have velocity dispersion profiles that are closer to isothermal than those of haloes with cores that are formed due to SNF in simulations with bursty star formation (impulsive cusp-core transformation). Impulsive SNF can generate positive stellar age gradients and increase random motion in the gas at the centre of the galaxy. Simulated galaxies in haloes with cores that were formed adiabatically are spatially more extended, with stellar metallicity gradients that are shallower (at late times) than those of galaxies in other simulations. Such observable properties of the gas and the stars, which indicate either an adiabatic or an impulsive evolution of the gravitational potential, may be used to determine whether observed cores in DM haloes are formed through DM self-interactions or in response to impulsive SNF.