The Evolution Of The Galaxy Luminosity Function And Luminosity Function Of Galaxies Of Different Density Environments

In this paper, we present the methodology of photometric redshift determination with the BATC I5-color system by using hyperz program. Both simulated galaxies and real galaxies with known redshifts were used to estimate the accuracy of redshifts inferred from the multicolor photometry. From the test with simulated galaxies, the uncertainty in the inferred redshifts is about 0.02 ~ 0.03 for a given range of photometric uncertainty of 0.05 ~ 0.10. The results with the 27 real galaxies are in good agreement with the simulated ones. The advantage of using BATC intermediate-band system to derive redshift is clear through the comparison with the UBVRI broad-band system. The accuracy in redshift determination with BATC system is mainly affected by the selection of filters and the photometric uncertainties in the observation. When we take the limiting magnitudes of the 15 filters into account, we find that redshift can be determined with good accuracy for galaxies with redshifts less than 0.5, using only filters with central wavelengths shorter than 6000A.Using galaxy sample observed by the BATC large-field multi-color sky survey and galaxy data of SDSS in the overlapped fields and by the photometric redshift technique, we study the restframe r'-band galaxy luminosity function as a function of redshift and large-scale environment, which is defined by isodensity contour with density contrast δρ/ρ. The data set is a composite sample of 25,181 galaxies with redshifts 0.03 ≤ z < 0.5 and r' < 21.5 mag. The redshifts are composed by three parts: 1) spectroscopic redshifts in SDSS for local and most luminous galaxies; 2) 20-color photometric redshifts derived from BATC and SDSS; 3) 5-color photometric redshifts in SDSS. Galaxy luminosity function is approximated by Schechter function. The large size and the large spanning range in redshift allow us to investigate the evolution of luminosity function. We find that the faint-end slope α steepens from -1.17 at z ~ 0.06 to -2.22 at z ~ 0.4, which is the natural consequence of hierarchical models of galaxy formation. By density environment luminosity functions differ distinctly also, α steepens from -1.01 at underdense regions to -1.30 at overdense regions and M brightens from -21.01 to -21.41. This suggests that large amount of faint galaxies live in high density regions.