2007ApJ...661..714C

We examine the properties of two galaxy ``halos'' at z∼0.7 in the Ton 153 (z<sub>em</sub>=1.01) quasar field. The first absorber-galaxy pair (G1) is a z=0.672, L<sub>B</sub>=4.3L<sup>*</sup><sub>B</sub>, E/S0 galaxy probed at D=58 kpc. G1 is associated with a remarkable five-component Lyα complex having τ<sub>LL</sub>≤0.4, W<sub>r</sub>(Lyα)=2.8 Å, and a velocity spread of Δv=1420 km/s. We find no Mg II, C IV, N V, nor O VI absorption in these clouds and infer metallicity upper limits of -3≤logZ/Z<sub>☉</sub>≤-1, depending on assumptions of photoionized or collisionally ionized gas. The second absorber-galaxy pair (G2) is a z=0.661, L<sub>B</sub>=1.8L<sup>*</sup><sub>B</sub>, Sab galaxy probed at D=103 kpc. G2 is associated with metal-enriched (logZ/Z<sub>☉</sub>≃-0.4) photoionized gas having N(HI)≃18.3 (/cm2) and a velocity spread of Δv=200 km/s. The very different G1 and G2 systems both have gas-galaxy properties inconsistent with the standard luminosity-dependent galaxy ``halo'' model commonly invoked for quasar absorption line surveys. We emphasize that mounting evidence is revealing that extended galactic gaseous envelopes in the regime of D≤100 kpc do not exhibit a level of homogeneity supporting a standardized halo model. Selection effects may have played a central role in the development of a simple model. We discuss the G1 and G2 systems in the context of ΛCDM models of galaxy formation and suggest that the heterogeneous properties of absorber-galaxy pairs is likely related to the range of overdensities from which galaxies and gas structures arise.