Numerical Simulations of Globular Cluster Formation

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Abstract
We examine various physical processes associated with the formation of globular clusters by using the three-dimensional smoothed particle hydrodynamics (SPH) code. Our code includes radiative cooling of gases, star formation, energy feedback by stars including stellar winds and supernovae, and chemical enrichment by stars. We assume that, in the collapsing galaxy, isothermal cold clouds form through thermal condensations and become proto-globular clouds. We calculate the size of proto-globular clouds by solving the linearized equations for perturbation. We compute the evolution of the inner region of the protocloud with our SPH code for various initial radius and initial composition of gases. When the initial gases contain no heavy elements, the evolution of protoclouds sensitively depends on the initial radius. For a smaller initial radius, the initial starburst is so intense that the subsequent star formation occurs in the central regions to form a dense star cluster as massive as the globular cluster. When the initial gases contain some heavy elements, the metallicity of gases affects the evolution and the final stellar mass. If the initial radius of the proto-globular clouds was relatively large, the formation of a star cluster as massive as the globular clusters requires the initial metallicity as high as [Fe/H] ≥ -2. The self-enrichment of heavy elements in the star cluster does not occur in all cases.