William J. Gray

FORMATION OF COMPACT STELLAR CLUSTERS BY HIGH-REDSHIFT GALAXY OUTFLOWS. I. NON-EQUILIBRIUM COOLANT FORMATION

We use high-resolution three-dimensional adaptive mesh refinement simulations to investigate the interaction of high-redshift galaxy outflows with low-mass virialized clouds of primordial composition. While atomic cooling allows star formation in objects with virial temperatures above 104 K, minihalos below this threshold are generally unable to form stars by themselves. However, these objects are highly susceptible to triggered star formation, induced by outflows from neighboring high-redshift starburst galaxies. Here, we conduct a study of these interactions, focusing on cooling through non-equilibrium molecular hydrogen (H2) and hydrogen deuteride (HD) formation. Tracking the non-equilibrium chemistry and cooling of 14 species and including the presence of a dissociating background, we show that shock interactions can transform minihalos into extremely compact clusters of coeval stars. Furthermore, these clusters are all less than 106 M ☉, and they are ejected from their parent dark matter halos: properties that are remarkably similar to those of the old population of globular clusters.

IDENTIFICATION OF A FUNDAMENTAL TRANSITION IN A TURBULENTLY SUPPORTED INTERSTELLAR MEDIUM

The interstellar medium (ISM) in star-forming galaxies is a multiphase gas in which turbulent support is at least as important as thermal pressure. Sustaining this configuration requires continuous radiative cooling, such that the overall average cooling rate matches the decay rate of turbulent energy into the medium. Here we carry out a set of numerical simulations of a stratified, turbulently stirred, radiatively cooled medium, which uncover a fundamental transition at a critical one-dimensional turbulent velocity of ≈35 km s–1. At turbulent velocities below ≈35 km s–1, corresponding to temperatures below 105.5 K, the medium is stable, as the time for gas to cool is roughly constant as a function of temperature. On the other hand, at turbulent velocities above the critical value, the gas is shocked into an unstable regime in which the cooling time increases strongly with temperature, meaning that a substantial fraction of the ISM is unable to cool on a turbulent dissipation timescale. This naturally leads to runaway heating and ejection of gas from any stratified medium with a 1D turbulent velocity above ≈35 km s–1, a result that has implications for galaxy evolution at all redshifts.

ATOMIC CHEMISTRY IN TURBULENT ASTROPHYSICAL MEDIA. I. EFFECT OF ATOMIC COOLING

We carry out direct numerical simulations of turbulent astrophysical media that explicitly track ionizations, recombinations, and species-by-species radiative cooling. The simulations assume solar composition and follows the evolution of hydrogen, helium, carbon, oxygen, sodium, and magnesium, but they do not include the presence of an ionizing background. In this case, the medium reaches a global steady state that is purely a function of the one-dimensional turbulent velocity dispersion,

ATOMIC CHEMISTRY in TURBULENT ASTROPHYSICAL MEDIA. II. EFFECT of the REDSHIFT ZERO METAGALACTIC BACKGROUND

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Formation of Compact Clusters from High Resolution Hybrid Cosmological Simulations

and the product of the mean density and the driving scale of turbulence,

Shadows of our Former Companions: How the Single-Degenerate Binary Type Ia Supernova Scenario Affects Remnants

n L.

The Effect of Turbulence on Nebular Emission Line Ratios

Our simulations span a grid of models with

Modeling Photoionized Turbulent Material in the Circumgalactic Medium

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Investigation of the hydrodynamics and emission of a laser heated tamped high-Z target

ranging from 6 to 58 km s

Effect of angular momentum alignment and strong magnetic fields on the formation of protostellar discs

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