Deviations from the Schmidt-Kennicutt relations during early galaxy evolution

Abstract

We utilize detailed time-varying models of the coupled evolution of stars and the HI, H_2, and CO-bright H_2 gas phases in galaxy-sized numerical simulations to explore the evolution of gas-rich and/or metal-poor systems, expected to be numerous in the Early Universe. The inclusion of the CO-bright H_2 gas phase, and the realistic rendering of star formation as an H_2-regulated process (and the new feedback processes that this entails) allows the most realistic tracking of strongly evolving galaxies, and much better comparison with observations. We find that while galaxies eventually settle into states conforming to Schmidt-Kennicutt (S-K) relations, significant and systematic deviations of their star formation rates (SFRs) from the latter occur, especially pronounced and prolonged for ... ...This indicates potentially serious limitations of (S-K)-type relations as reliable sub-grid elements of star formation physics in simulations of structure formation in the Early Universe. We anticipate that galaxies with marked deviations from the S-K relations will be found at high redshifts as unbiased inventories of total gas mass become possible with ALMA and the EVLA.