A Near‐Solar Metallicity, Nitrogen‐deficient Lyman Limit Absorber Associated with Two S0 Galaxies

From UV spectra of the bright quasar PHL 1811 recorded by FUSE and the E140Mconfiguration on STIS, we have determined the abundances of various atomicspecies in a Lyman limit system at z = 0.0809 with log N(H I) = 17.98.Considerably more hydrogen may be in ionized form, since the abundances of CII, Si II, S II and Fe II are very large compared to that of O I, when comparedto their respective solar abundance ratios. Our determination [O/H] = -0.19 inthe H I-bearing gas indicates that the chemical enrichment of the gas isunusually high for an extragalactic QSO absorption system. However, this samematerial has an unusually low abundance of nitrogen, [N/O] < -0.59, indicatingthat there may not have been enough time during this enrichment for secondarynitrogen to arise from low and intermediate mass stars. In an earlierinvestigation we found two galaxies at nearly the same redshift as thisabsorption system and displaced by 34 and 87 kpc from the line of sight. Anr-band image recorded by the ACS on HST indicates these are S0 galaxies. One orboth of these galaxies may be the source of the gas, which might have beenexpelled in a fast wind, by tidal stripping, or by ram-pressure stripping.Subtraction of the ACS point-spread function from the image of the QSO revealsthe presence of a face-on spiral galaxy under the glare of the quasar; althoughit is possible that this galaxy may be responsible for the Lyman limitabsorption, the exact alignment of the QSO with the center of the galaxysuggests that the spiral is the quasar host.