THE NATURE AND ORIGIN OF Z(A)APPROXIMATE-TO-Z(E) ABSORPTION-LINES IN THE REDSHIFT 0.20 QUASAR, PKS-2135-147

We use new UV and optical spectra and an archival Hubble Space Telesco pe Wide Field Planetary Camera 2 (HST-WFPC2) image to study the z(a) a pproximate to z(e) absorber in the z(e) approximate to 0.20 QSO PKS 21 35-147. The UV spectra, obtained with the Faint Object Spectrograph on HST, show strong z(a) approximate to z(e) absorption lines of C IV, N V, O VI, Ly alpha, and Ly beta. The z(a) approximate to z(e) line pro files are resolved, with deconvolved FWHM of 270-450 km s(-1). The Lym an decrement and the O VI and N V doublet ratios indicate that there a re also narrower, optically thick line components, and there is eviden ce in the C IV and Ly alpha profiles for two blended components. Lower limits on the total column densities are of order 10(15) cm(-2) for a ll ions. The similar to 2:1 ratio of the C IV doublets suggests that t he total C IV column density is near the lower limit. If the absorber is photoionized by the QSO and the derived relative columns in C IV an d H I are roughly correct, then the metallicity must be at least solar . The location of the z(a) approximate to z(e) absorber remains uncert ain. The line redshifts indicate that the clouds have little radial mo tion (less than +/- 200 km s(-1)) with respect to the QSO. This small velocity shift could mean that the absorber is outside of the deep gra vitational potential of the QSO and the host-galaxy nucleus. Two simil ar to L- galaxies in a small cluster centered on PKS 2135-147 lie wit hin 36 h(-1) kpc projected distance and have redshifts consistent with causing or contributing to the z(a) approximate to z(e) lines. The ex tensive halo of the QSO's host galaxy could also contribute. Calculati ons show that the QSO is bright enough to photoionize gas up to O VI i n the low-density halos of the host and nearby cluster galaxies. Nonet heless, there is indirect evidence for absorption much nearer the QSO, namely (1) the derived high (albeit uncertain) metallicity; (2) the r elatively strong N v-absorption lines, which might be caused by a high er nitrogen abundance in the metal-rich gas; and (3) strong, lobe-domi nated, steep-spectrum radio emission, which is known to correlate with a much higher incidence of(probably intrinsic) z(a) approximate to z( e) lines. We propose that the C IV/N V/O VI line ratios can be used as a general diagnostic of intrinsic versus intervening absorption, as l ong as the line saturation effects are understood.