Publication Date:
2013-09-26
Description:
We present a census of z abs 2 intrinsic (those showing partial coverage) and associated ( z abs ~ z em ) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 〈 z em 〈 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N v intrinsic systems (where the equivalent width of H i Lyα is small compared to N v 1238) presented in that work, but find no convincing cases of ‘strong C iv ’ intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of ‘strong O vi ’ systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N v ion have the highest probability of being intrinsic. By contrast, the C iv and O vi ions are poor selectors. Of the 30 O vi systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ~3 excess in the number of absorbers near the quasar redshift (| v | ≤ 5000 km s –1 ) over absorbers at large redshift differences. In at least two cases, the associated O vi systems are known not to arise close to the accretion disc of the quasar.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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