2002ApJ...574L.115M

We have conducted pointed redshift surveys for galaxies in the direction of bright active galactic nuclei whose Hubble Space Telescope far-UV spectra contain nearby (cz≲30,000 km.s^–1), low column density [12.5≤logN_HI_(cm^–2)≤14.5] Lyα forest absorption systems. Here we present results for four lines of sight that contain nearby (cz≲3000 km.s^–1) Lyα absorbers in galaxy voids. Although our data go quite deep [-13≤M_B(limit)≤-14] out to impact parameters of ρ≲100-250 h^–1₇₀ kpc, these absorbers remain isolated and thus appear to be truly intergalactic, rather than part of galaxies or their halos. Since we and others have discovered no galaxies in voids, the only baryons detected in the voids are in the Lyα ``clouds.'' Using a photoionization model for these clouds, the total baryonic content of the voids is 4.5%±1.5% of the mean baryon density.