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Discovery of z=0.0912 and z=0.2212 Damped Lyman-alpha Absorption Line Systems Toward the Quasar OI 363: Limits on the Nature of Damped Lyman-alpha Galaxies

Sandhya M. Rao·David A. Turnshek
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Abstract

The discovery of a z_abs = 0.0912 damped Lyman-alpha absorption-line system in the HST-FOS ultraviolet spectrum of the quasar OI 363 (0738+313) is reported. This is the lowest redshift quasar damped Lyman-alpha system known. Its neutral hydrogen column density is N(HI) = 1.5(+/- 0.2) E21 atoms/cm^2, which easily exceeds the classical criterion for damped Lyman-alpha of N(HI) greater than or equal to 2E20 atoms/cm^2. Remarkably, a z_abs = 0.2212 damped system with N(HI) = 7.9(+/- 1.4) E20 atoms/cm^2 has also been discovered in the same spectrum. In the past, the standard paradigm for damped Lyman-alpha systems has been that they arise in galactic or protogalactic HI disks with low impact parameters in luminous galaxies. However, WIYN imaging of the OI 363 field shows that none of the galaxies visible in the vicinity of the quasar is a luminous gas-rich spiral with low impact parameter, either at z = 0.0912 or z = 0.2212. Thus, these damped systems are among the clearest examples yet of cases that are inconsistent with the standard damped Lyman-alpha - HI-disk paradigm.

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Sandhya M. Rao, David A. Turnshek. 1998-05-07. Discovery of z=0.0912 and z=0.2212 Damped Lyman-alpha Absorption Line Systems Toward the Quasar OI 363: Limits on the Nature of Damped Lyman-alpha Galaxies. https://doi.org/10.1086/311411

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