Modeling high-redshift galaxies: what can we learn from high and ultra-high resolution hydrodynamical simulations?

We present results from a high resolution cosmological galaxy formation simulation called Mare Nostrum and a ultra-high resimulation of the first 500 million years of a single, Milky Way (MW) sized galaxy. Using the cosmological run, we measure UV luminosity functions and assess their sensitivity to both cosmological parameters and dust extinction. We find remarkably good agreement with the existing data over the redshift range 4 < z < 7 provided we adopt the favoured cosmology (WMAP 5 year parameters) and a self-consistent treatment of the dust. Cranking up the resolution, we then study in detail a z = 9 protogalaxy sitting at the intersection of cold gas filaments. This high-z MW progenitor grows a dense, rapidly spinning, thin disk which undergoes gravitational fragmention. Star formation in the resulting gas clumps rapidly turns them into globular clusters. A far reaching galactic wind develops, co-powered by the protogalaxy and its cohort of smaller companions populating the filaments. Despite such an impressive blow out, the smooth filamentary material is hardly affected at these redshifts.

Some Problems in Winding Geometry

The efficiency of wound, hollow-fiber separation modules used to remove dissolved salts from water by the process of reverse osmosis may be improved by alterations in module geometry. Normally, the hollow-fiber membranes composing the module are helically wound about a cylindrical core. Flow rate through the module may be increased, however, if the cross-sectional density of wound fibers varies uniformly along the module axis. This paper explores the analytical requirements for the helical winding of a conical mandrel with filamentary material in a manner that eventually produces a cylindrically shaped package. The effect of specifying either a constant yarn feed rate or a constant spindle speed during winding is considered in relation to restrictions on the length of material added per circuit.