2007ApJ...661..714C -
Astrophys. J., 661, 714-718 (2007/June-1)
On the heterogeneity of metal-line and Lyα absorption in galaxy ``Halos'' at z ∼ 0.7.
CHURCHILL C.W., KACPRZAK G.G., STEIDEL C.C. and EVANS J.L.
Abstract (from CDS):
We examine the properties of two galaxy ``halos'' at z∼0.7 in the Ton 153 (zem=1.01) quasar field. The first absorber-galaxy pair (G1) is a z=0.672, LB=4.3L*B, E/S0 galaxy probed at D=58 kpc. G1 is associated with a remarkable five-component Lyα complex having τLL≤0.4, Wr(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☉≤-1, depending on assumptions of photoionized or collisionally ionized gas. The second absorber-galaxy pair (G2) is a z=0.661, LB=1.8L*B, Sab galaxy probed at D=103 kpc. G2 is associated with metal-enriched (logZ/Z☉≃-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.
Abstract Copyright:
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Journal keyword(s):
Galaxies: Quasars: Absorption Lines - quasars: individual (QSO B1317+274)
Nomenclature:
Fig.1: [CKS2007] GN (Nos G1-G2).
Simbad objects:
2
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