The properties of galaxies in voids

PATIRI, SANTIAGO G.; PRADA, FRANCISCO; HOLTZMAN, JON; KLYPIN, ANATOLY; BETANCORT-RIJO, JUAN

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Año: 2006 vol. 372 p. 1710 - 1720

0035-8711

We present a comparison of the properties of galaxies in the most underdense regions of the Universe, where the galaxy number density is less than 10 per cent of the mean density, with galaxies from more typical regions. We have compiled a sample of galaxies in 46 large nearby voids that were identified using the Sloan Digital Sky Survey DR4, which provides the largest coverage of the sky. We study the u - r colour distribution, morphology, specific star formation rate (SFR) and radial number density profiles for a total of 495 galaxies fainter than M_r = -20.4 + 5 logh located inside the voids and compare these properties with a control sample of field galaxies. We show that there is an excess of blue galaxies inside the voids. However, inspecting the properties of blue and red galaxies separately, we find that galaxy properties such as colour distribution, bulge-to-total ratios and concentrations are remarkably similar between the void and overall sample. The void galaxies also show the same specific SFR at fixed colour as the control galaxies. We compare our results with the predictions of cosmological simulations of galaxy formation using the Millennium Run semi-analytic galaxy catalogue. We show that the properties of the simulated galaxies in large voids are in reasonably good agreement with those found in similar environments in the real Universe. To summarize, in spite of the fact that galaxies in voids live in the least dense large-scale environment, this environment makes very little impact on the properties of galaxies.