The BAL Quasar Q\,0059-2735

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Session 34 -- Spectroscopy of AGN II: Broad Lines and Spectral Evolution
Oral presentation, Monday, 9, 1995, 2:00pm - 3:30pm

[34.02] The BAL Quasar Q\,0059-2735

J. Wampler (ESO), N. Chugai (Inst. of Astr. Moscow), P. Petitjean (IAP Paris)

Spectra of the BAL quasar Q\,0059$-$2735 show that absorption features are formed both in a BAL flow and in low velocity clouds. The low velocity clouds produce narrow ($b$\ {\raise-.5ex\hbox{$\buildrel<\over\sim$}} \,20\,km\,s$^{-1}$), saturated lines with substantial absorption from metastable levels. Our analysis shows that the narrow absorption line clouds lie only a few parsecs from the QSO nucleus. Level populations imply excitation temperatures of $\sim10^4$\,K for the NAL clouds and up to 6\,$10^4$\,K for the BAL clouds. The high ionization BAL flow occults the central continuum sources of Q\,0059$-$2735 as well as the high ionization emission-line region. While the low ionization BAL absorption also occults the nuclear continuum sources, the broad, low ionization emission-line, regions are not covered. Like the BAL clouds, the NAL clouds also cover little of the low ionization, broad emission-line cloud region. But, in contrast to the BAL clouds, the NAL clouds cover only about 50\% of the continuum radiation in the $\lambda\lambda\,1800-2800$\,\AA\ region. While conditions differ somewhat, both the NAL and BAL clouds have very thin H\,{\sc i}~layers, with ionized column densities exactly equal to the Str\"{o}mgren column density. The relative thickness of H\,{\sc i}~layer can only be of the order of $10^{-2}N_{\rm S}$; a fact that strongly suggests the existence of a fine-tuning mechanism for removal of excessive H\,{\sc i}~material in the Lyman continuum shadow. Our abundance analysis of BAL flow gives a Fe overabundant by factor of about 10 relative to carbon. The chemical abundance of material so close to a high redshift quasar nucleus is of great interest and needs to be re-examined using spectra with lower noise than those now available to us. Our spectra suggests a model in which metal rich, low ionization gas condensations are being ablated by the intense radiation field of the Q\,0059$-$2735 nucleus. The covering pattern of the absorption-lines in the spectrum of Q\,0059$-$2735 supports the idea that the nuclear region is hierarchical, with the non-thermal continuum region being smaller than the broad emission-line regions and the high-ionization emission clouds being less extended the low-ionization emission clouds.

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