A Summary of the Properties of Zabs > Zem Systems and Some Comments on the Origins of QSO Absorption Line Systems

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Abstract
Z abs > Z em systems are "real" in the sense of not being artifacts of measuring errors, but Z em may not represent the true Z of the QSO. However, a specific simple model involving occultation of outflowing gas by an opaque central object produces too much asymmetry in the emission lines. If Z abs > Z QSO systems truly exist the least objectionable model involves clouds of gas bound in an associated large cluster. Lack of detectable C II fine structure in 3 objects (1225+31, 1331+17, 1756+23) suggests the absorbing material is ≳ 500 kpc from the QSO on the basis of ionization arguments, leading to unacceptably large kinetic energies if the absorption is "intrinsic". Defects in the ionization argument are considered. Preliminary statistical results on low Z ab Mg II systems require that the effective radius for producing such systems by intervening galaxies must be ∼ 5 times the Holmberg radius, but attempts to detect such galaxies have not been successful. Finally, it is speculated that a correlation may exist between the column density of the strongest absorption system and multiplicity of absorption systems in a given object suggesting that systems like those in 1756+23 are intrinsic, despite the C II fine-structure argument.