NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T10:40:59 PDT
Help | Comment | NED Home

For refcode 2005ApJ...635..123P:
Retrieve 6569 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2005ApJ...635..123P The SDSS Damped Ly{alpha} Survey: Data Release 3 Jason X. Prochaska, Stephane Herbert-Fort, and Arthur M. Wolfe Abstract. We present the results from a damped Ly{alpha} survey of the Sloan Digital Sky Survey, Data Release 3. We have discovered over 500 new damped Ly{alpha} systems at z>2.2, and the complete statistical sample for z>1.6 has more than 600 damped Ly{alpha} galaxies. We measure the H I column density distribution f_HI_(N, X) and its zeroth and first moments (the incidence l_DLA_ and gas mass density {OMEGA}^DLA^_g_ of damped Ly{alpha} 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 {GAMMA} function (or double power law) with "break" column density N_{gamma}_=10^21.5+/-0.1^cm^-2^ and "faint-end" slope {alpha}=-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 Ly{alpha} 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 Ly{alpha} analysis and identify only one important effect: we measure 40%+/-20% higher {OMEGA}^DLA^_g_ values 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 {LAMBDA}CDM, we find that all of the models significantly underpredict l_DLA_ at z=3, and only SPH models with significant feedback can reproduce {OMEGA}^DLA^_g_ at high redshift. Based on our results for the damped Ly{alpha} 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_<10^20^cm^-2^ has an inflection with slope d log f/d log N>-1. We advocate a new mass density definition, the mass density of predominantly neutral gas {OMEGA}^neut^_g_, to be contrasted with the mass density of gas associated with H I atoms. We contend the damped Ly{alpha} systems contribute >80% of {OMEGA}^neut^_g_ at all redshifts and therefore are the main reservoirs for star formation. Key words: Galaxies: Evolution, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines
Retrieve 6569 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home