Reporting a deficit of intrinsic Nv absorbers in core-dominated radio-loud quasars

We searched the Hubble Space Telescope Cosmic Origins Spectrograph archive for ultraviolet spectra of 428 active galactic nuclei (AGNs) to identify intrinsic Nv absorption systems. We filtered out Type 2 AGNs, blazars, and spectra that do not cover at least part of the velocity window from 5000km s^-1 blueward to 5000km s^-1 redward (hereafter, the ‘associated’ region) of the Nv emission line. This yielded 175 Type 1 quasars, 34 radio-loud, 133 radio-quiet, and eight unconstrained. Our survey uncovered 77 associated Nv systems in the spectra of 48 of these low-redshift quasars. We consider the incidence of intrinsic absorbers as a function of quasar properties (optical, radio and X-ray). We find a statistically significant dearth of intrinsic Nv systems in the spectra of the 34 radio-loud quasars (6 percent), compared to 29 percent of the 133 radio-quiet quasars containing at least one intrinsic system. Assuming intrinsic systems are equally likely to occur in radio-loud and radio-quiet quasars and the orientations of the two subsamples are comparable, there is a 0.1 per cent probability of such a deficit occurring by chance in the radio-loud population. We propose that this deficit of systems is caused by orientation effects. Faint Images of the Sky at 20-cm survey radio images are available for 14 of the 33 radio-loud quasars. These show that only three of the 14 radio-loud quasars have lobe-dominated morphologies, whereas 11 of the 14 radio-loud quasars have compact radio morphologies, implying that these quasars are face on, and suggesting that clouds that produce Nv absorption are rarely found along the polar axis.