Effect of Reionization on Structure Formation in the Universe

I use the simulations of cosmological reionization to quantify the effect ofthe gas fraction suppression in the low density objects due to photoionization.I show that the Jeans mass does not match the characteristic mass scale belowwhich the gas is efficiently expelled from the shallow potential wells, andwhich can be orders of magnitude lower that the Jeans mass. Instead, thefiltering mass, that directly corresponds to the filtering scale over which thebaryonic perturbations are smoothed in the linear theory, provides a remarkablygood fit to the characteristic mass scale. I also derive the full shape of theprobability distribution to find an object with a given gas mass among all theobjects with the same total mass which depends exclusively on the filteringmass. The proposed probability distribution may be useful for semi-analyticalmodeling of structure formation in the universe.