Photometric Properties of Void Galaxies in the Sloan Digital Sky Survey

Using a nearest neighbor analysis, we construct a sample of void galaxiesfrom the Sloan Digital Sky Survey (SDSS) and compare the photometric propertiesof these galaxies to the population of non-void (wall) galaxies. We trace thedensity field of galaxies using a volume-limited sample with z_{max}=0.089.Galaxies from the flux-limited SDSS with z\leq z_{max} and fewer than threevolume-limited neighbors within 7h^{-1}Mpc are classified as void galaxies.This criterion implies a density contrast \delta \rho/ \rho < -0.6 around voidgalaxies. From 155,000 galaxies, we obtain a sub-sample of 13,742 galaxies withz\leq z_{max}, from which we identify 1,010 galaxies as void galaxies. Toidentify an additional 194 faint void galaxies from the SDSS in the nearbyuniverse, r~ 72 h^{-1}Mpc, we employ volume-limited samples extracted from theUpdated Zwicky Catalog and the Southern Sky Redshift Survey with z_{max}=0.025to trace the galaxy distribution. Our void galaxies span a range of absolutemagnitude from M_r=-13.5 to M_r=-22.5. Using SDSS photometry, we compare thecolors, concentration indices, and Sersic indices of the void and wall samples.Void galaxies are significantly bluer than galaxies lying at higher density.The population of void galaxies with M_r ~ M* +1 and brighter is on averagebluer and more concentrated (later type) than galaxies outside of voids. Thelatter behavior is only partly explained by the paucity of luminous redgalaxies in voids. These results generally agree with the predictions ofsemi-analytic models for galaxy formation in cold dark matter models, whichindicate that void galaxies should be relatively bluer, more disklike, and havehigher specific star formation rates.Comment: Accepted for publication in Ap