THE OPTICAL LUMINOSITY FUNCTION OF VOID GALAXIES IN THE SDSS AND ALFALFA SURVEYS

We measure the r-band galaxy luminosity function(LF) across environments over the redshift range 0<$z$<0.107 using the SDSS. We divide our sample into galaxiesresiding in large scale voids ( void galaxies) and those residing in denser regions (wall galaxies). The best fitting Schechter parameters for void galaxiesare: log$\Phi^*$= -3.40$\pm$0.03 log(Mpc$^{-3}$), $M^*$= -19.88$\pm$0.05, and $\alpha$=-1.20$\pm$0.02. For wall galaxies, the best fitting parameters are: log$\Phi^*$=-2.86$\pm$0.02 log(Mpc$^{-3}$), $M^*$=-20.80$\pm$0.03, and $\alpha$=-1.16$\pm$0.01. We find a shift in the characteristic magnitude, $M^*$, towards fainter magnitudes for void galaxiesand find no significant difference between the faint-end slopes of the void and wall galaxyLFs. We investigate how low surface brightnessselections effects can affect the galaxyLF. To attempt to examine a sample of galaxiesthat is relatively free of surface brightnessselection effects, we compute the optical galaxyLF of galaxiesdetected by the blind HI survey, ALFALFA. We find that the global LF of the ALFALFA sample is not well fit by a Schechter function, because of the presence of a wide dip in the LF around $M_r$=-18 and an upturn at fainter magnitudes ($\alpha$~-1.47). We compare the HI selected r-band LF to various LFs of optically selected populations to determine where the HI selected optical LF obtains its shape. We find that sample selection plays a large role in determining the shape of the LF.