SIMBAD references

We present the results from a damped Lyα survey of the Sloan Digital Sky Survey, Data Release 3. We have discovered over 500 new damped Lyα systems at z>2.2, and the complete statistical sample for z>1.6 has more than 600 damped Lyα galaxies. We measure the H I column density distribution f_HI(N, X) and its zeroth and first moments (the incidence ℓ_DLAand gas mass density Ω^DLA_gof damped Lyα systems, respectively) as a function of redshift. The key results include: (1) the full SDSS DR3 f_HI(N, X) distribution (z∼3.06) is well fit by a Γ function (or double power law) with ``break'' column density N<sub>γ</sub>=10<sup>21.5±0.1</sup>/cm2 and ``faint-end'' slope α=-1.8±0.1; (2) the shape of the f_HI(N, X) distributions in a series of redshift bins does not show evolution; (3) the incidence and gas mass density of damped systems decrease by 35%±9% and 50%±10% during ~1 Gyr between the redshift intervals z=[3.0, 3.5] and z=[2.2, 2.5]; and (4) the incidence and gas mass density of damped Lyα systems in the lowest SDSS redshift bin (z=2.2) are consistent with the current values. We investigate a number of systematic errors in damped Lyα analysis and identify only one important effect: we measure 40%±20% higher Ω^DLA_gvalues toward a subset of brighter quasars than toward a faint subset. This effect is contrary to the bias associated with dust obscuration and suggests that gravitational lensing may be important. Comparing the results against several models of galaxy formation in ΛCDM, we find that all of the models significantly underpredict ℓ_DLAat z=3, and only SPH models with significant feedback can reproduce Ω^DLA_gat high redshift. Based on our results for the damped Lyα systems, we argue that the Lyman limit systems contribute ~33% of the universe's H I atoms at all redshifts z=2-5. Furthermore, we infer that the f_HI(N, X) distribution for N_HI_<10²⁰/cm2 has an inflection with slope dlogf/dlogN>-1. We advocate a new mass density definition, the mass density of predominantly neutral gas Ω^neut_g, to be contrasted with the mass density of gas associated with H I atoms. We contend the damped Lyα systems contribute >80% of Ω^neut_g at all redshifts and therefore are the main reservoirs for star formation.