Evolution of Galaxy Luminosity Function and Luminosity Function by Density Environment at 0.03<z<0.5

Using galaxy sample observed by the BATC large-field multi-color sky survey and galaxy data of SDSS in the overlapped fields, we study the dependence of the restframe $r$-band galaxy luminosity function on redshift and on large-scale environment. The large-scale environment is defined by isodensity contour 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 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. We find that the faint-end slope \alpha steepens slightly from -1.21 at z ~ 0.06 to -1.35 at z ~ 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 at underdense regions to -1.37 at overdense regions and the corresponding M* 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.Comment: 7 pages, 9 figures, accepted by Ap

Metallicities of Emission-Line Galaxies from HST ACS PEARS and HST WFC3 ERS Grism Spectroscopy at 0.6 < z < 2.4

Galaxies selected on the basis of their emission line strength show low metallicities, regardless of their redshifts. We conclude this from a sample of faint galaxies at redshifts between 0.6 < z < 2.4, selected by their prominent emission lines in low-resolution grism spectra in the optical with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) and in the near-infrared using Wide-Field Camera 3 (WFC3). Using a sample of 11 emission line galaxies (ELGs) at 0.6 < z < 2.4 with luminosities of -22 < M_B < -19, which have [OII], H\beta, and [OIII] line flux measurements from the combination of two grism spectral surveys, we use the R23 method to derive the gas-phase oxygen abundances: 7.5 < 12+log(O/H) < 8.5. The galaxy stellar masses are derived using Bayesian based Markov Chain Monte Carlo (\piMC^2) fitting of their Spectral Energy Distribution (SED), and span the mass range 8.1 < log(M_*/M_\sun) < 10.1. These galaxies show a mass-metallicity (M-L) and Luminosity-Metallicity (L-Z) relation, which is offset by --0.6 dex in metallicity at given absolute magnitude and stellar mass relative to the local SDSS galaxies, as well as continuum selected DEEP2 samples at similar redshifts. The emission-line selected galaxies most resemble the local "green peas" galaxies and Lyman-alpha galaxies at z~0.3 and z~2.3 in the M-Z and L-Z relations and their morphologies. The G-M_{20} morphology analysis shows that 10 out of 11 show disturbed morphology, even as the star-forming regions are compact. These galaxies may be intrinsically metal poor, being at early stages of formation, or the low metallicities may be due to gas infall and accretion due to mergers.Comment: 24 pages with 7 figure