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Current models of galaxy formation require strong feedback from active galactic nuclei (AGN) to explain the observed lack of star formation in massive galaxies sincez≈ 2, but direct evidence of this energy input is limited. We use the SIMBA cosmological galaxy formation simulations to assess the ability of thermal Sunyaev–Zel’dovich (tSZ) measurements to provide such evidence, by mapping the pressure structure of the circumgalactic medium around massivez≈ 0.2–1.5 galaxies. We undertake a stacking approach to calculate the total tSZ signal and its radial profile in simulations with varying assumptions of AGN feedback, and we assess its observability with current and future telescopes. By convolving our predictions with the 2.′1 beam of the Atacama Cosmology Telescope, we show that current observations atz≈ 1 are consistent with SIMBA’s fiducial treatment of AGN feedback and inconsistent with SIMBA models without feedback. Atz≈ 0.5, observational signals lie between SIMBA run with and without AGN feedback, suggesting AGN in SIMBA may inject too much energy at late times. By convolving our data with a 9.″5 beam corresponding to the TolTEC camera on the Large Millimeter Telescope Alfonso Serrano, we predict a unique profile for AGN feedback that can be distinguished with future higher-resolution measurements. Finally, we explore a novel approach to quantify the nonspherically symmetric features surrounding our galaxies by plotting radial profiles representing the component of the stack with m-fold symmetry.

 

The recently launched James Webb Space Telescope promises unparalleled advances in our understanding of the first stars and galaxies, but realizing this potential requires cosmological simulations that capture the key physical processes that affected these objects. Here, we show that radiative transfer and subgrid turbulent mixing are two such processes. By comparing simulations with and without radiative transfer but with exactly the same physical parameters and subgrid turbulent mixing model, we show that tracking radiative transfer suppresses the Population III star formation density by a factor ≈4. In both simulations, ≳90% of Population III stars are found in the unresolved pristine regions tracked by our subgrid model, which does a better job at modeling the regions surrounding proto-galaxy cores where metals from supernovae take tens of megayears to mix thoroughly. At the same time, radiative transfer suppresses Population III star formation, via the development of ionized bubbles that slow gas accretion in these regions, and it results in compact high-redshift galaxies that are surrounded by isolated low-mass satellites. Thus, turbulent mixing and radiative transfer are both essential processes that must be included to accurately model the morphology, composition, and growth of primordial galaxies.

 

Absorption-line measurements of the circumgalactic medium (CGM) display a highly nonuniform distribution of lower ionization state species accompanied by more widespread higher ionization state material. This suggests that the CGM is a dynamic, multiphase medium, such as arises in the presence of turbulence. To better understand this evolution, we perform hydrodynamic and magnetohydrodynamic (MHD) simulations of the CGM surrounding Milky Way–like galaxies. In both cases, the CGM is initially in hydrostatic balance in a 10¹²M_⊙dark matter gravitational potential, and the simulations include rotation in the inner halo and turbulence that decreases radially. They also track ionizations, recombinations, and species-by-species radiative cooling in the presence of the redshift-zero UV background, employing the MAIHEM nonequilibrium chemistry package. We find that after 9 Gyr of evolution, the presence of a magnetic field leads to an overall hotter CGM, with cool gas in the center where magnetic pressure dominates. While the non-MHD run produces more cold clouds overall, we find similar Siiv/Oviand Nv/Oviratios between the MHD and non-MHD runs, which are both very different from their equilibrium values. The non-MHD halo develops cool, low angular momentum filaments above the central disk, in comparison to the MHD run that has more efficient angular momentum transport, especially for the cold gas, which forms a more ordered and extended disk late into its evolution.

 

Although galactic winds play a critical role in regulating galaxy formation, hydrodynamic cosmological simulations do not resolve the scales that govern the interaction between winds and the ambient circumgalactic medium (CGM). We implement the Physically Evolved Wind (PhEW) model of Huang et al. in the gizmo hydrodynamics code and perform test cosmological simulations with different choices of model parameters and numerical resolution. PhEW adopts an explicit subgrid model that treats each wind particle as a collection of clouds that exchange mass and metals with their surroundings and evaporate by conduction and hydrodynamic instabilities as calibrated on much higher resolution cloud scale simulations. In contrast to a conventional wind algorithm, we find that PhEW results are robust to numerical resolution and implementation details because the small scale interactions are defined by the model itself. Compared to our previous wind simulations with the same resolution, our PhEW simulations are in better agreement with low-redshift galactic stellar mass functions at M* < 1011M⊙ because PhEW particles shed mass to the CGM before escaping low mass haloes. PhEW radically alters the CGM metal distribution because PhEW particles disperse metals to the ambient medium as their clouds dissipate, producing a CGM metallicity distribution that is skewed but unimodal and is similar between cold and hot gas. While the temperature distributions and radial profiles of gaseous haloes are similar in simulations with PhEW and conventional winds, these changes in metal distribution will affect their predicted UV/X-ray properties in absorption and emission.

 

ABSTRACT The propagation and evolution of cold galactic winds in galactic haloes is crucial to galaxy formation models. However, modelling of this process in hydrodynamic simulations of galaxy formation is oversimplified owing to a lack of numerical resolution and often neglects critical physical processes such as hydrodynamic instabilities and thermal conduction. We propose an analytic model, Physically Evolved Winds, that calculates the evolution of individual clouds moving supersonically through a uniform ambient medium. Our model reproduces predictions from very high resolution cloud-crushing simulations that include isotropic thermal conduction over a wide range of physical conditions. We discuss the implementation of this model into cosmological hydrodynamic simulations of galaxy formation as a subgrid prescription to model galactic winds more robustly both physically and numerically.