Evolution of the galaxy luminosity function for redshift and density environment at 0.03<z<0.5

Using the galaxy sample observed by the Beijing- Arizona- Taiwan- Connecticut ( BATC) large- field multicolor sky survey and the galaxy data of the Sloan Digital Sky Survey ( SDSS) in overlapping fields, we study the dependence of the rest-frame r- band galaxy luminosity function on redshift and on the large- scale environment. The large- scale environment is defined by isodensity contours with density contrast delta rho/rho. The data set is a composite sample of 69,671 galaxies with redshifts 0:03 < z < 0: 5 and r < 21:5 mag. The redshift data are composed of three parts: (1) spectroscopic redshifts in SDSS for local and the most luminous galaxies, ( 2) 20-color photometric redshifts derived from BATC and SDSS, and (3) five-color photometric redshifts in SDSS. We find that the faint-end slope alpha steepens slightly from -1.21 at z similar to 0: 06 to - 1.35 at z similar to 0: 4, which is the natural consequence of the hierarchical formation of galaxies. The luminosity function also differs with different environments. The value of alpha changes from -1.21 in underdense regions to -1.37 in overdense regions, and the correspondingM(*) brightens from -22.26 to -22.64. This suggests that the fraction of faint galaxies is larger in high- density regions than in low- density regions.