Cosmological Evolution of Supergiant Star‐forming Clouds

In an exploration of the birthplaces of globular clusters, we present acareful examination of the formation of self-gravitating gas clouds withinassembling dark matter haloes in a hierarchical cosmological model. Ourhigh-resolution smoothed particle hydrodynamical simulations are designed todetermine whether or not hypothesized supergiant molecular clouds (SGMCs) formand, if they do, to determine their physical properties and mass spectra. Itwas suggested in earlier work that clouds with a median mass of several 10^8M_sun are expected to assemble during the formation of a galaxy, and thatglobular clusters form within these SGMCs. Our simulations show that cloudswith the predicted properties are indeed produced as smaller clouds collide andagglomerate within the merging dark matter haloes of our cosmological model. Wefind that the mass spectrum of these clouds obeys the same power-law formobserved for globular clusters, molecular clouds, and their internal clumps ingalaxies, and predicted for the supergiant clouds in which globular clustersmay form. We follow the evolution and physical properties of gas clouds withinsmall dark matter haloes up to z = 1, after which prolific star formation isexpected to occur. Finally, we discuss how our results may lead to morephysically motivated "rules" for star formation in cosmological simulations ofgalaxy formation.Comment: Accepted to The Astrophysical Journal; 17 pages, 8 figure