An analysis of the spectrum of the large-redshift quasi-stellar object OQ 172

The quasi-stellar object OQ 172, with z = 3.53, has been observed in detail with the image-dissector spectrum scanner on the Lick 120-inch (3-m) telescope. A list is given of 175 absorption lines; considerable line blending is still present. Analysis of the absorption lines shows that multiple redshift systems are present. The bestdetermined system, at z = 3.066, has lines from excited fine-structure levels in the ground states of Si ii and C ii. Other possible systems have z = 2.564, and close pairs at z = 3.094, 3.089 and 2.698, 2.691. Lyman lines at a very large number of discrete redshifts may be present. There is no detectable absorption at the Lyman limit at the emission-line redshift, and L if present is quite weak. The absorption-line systems also show little Lyman continuum absorption. Some limits are derived on the thickness, density, and distance from the central source of the absorbing clouds. Subject headings: line identifications - quasi-stellar sources or objects - redshifts