An Unusual “Mini-BAL” Quasar at [CLC][ITAL]z[/ITAL][/CLC] = 4.59

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Abstract
The z = 4.591 quasar PC 1415+3408 exhibits very strong associated metal-line absorption from the N V λλ1238, 1242, Si IV λλ1393, 1402, and C IV λλ1548, 1550 doublets spanning the velocity interval-1700 km s-1 ≤ v ≤ 0 km s-1. Also present are detached absorption troughs in N V and C IV spanning -5000 km s-1 ≤ v ≤ -3000 km s-1; this is characteristic of broad absorption line (BAL) quasars, but the small overall velocity spread suggests that PC 1415+3408 be classified as a "mini-BAL" quasar. The N V doublet is consistent with black saturation over the velocity interval -1200 to -500 km s-1; black N V absorption is extraordinary in all classes of quasars at all redshifts. Over this velocity interval, the C IV doublet is severely blended but also consistent with black saturation. The material over this range of velocity appears to fully occult the continuum source, the broad emission line region, and any material that could give rise to scattered light. In view of a unified scenario for BAL and mini-BAL absorption, these facts imply that the quasar is being viewed along a preferred direction. On the other hand, the black mini-BALs in PC 1415+3408 could be explained if the BAL flow has an unusual geometry compared with the population of BAL quasars and/or the spatial extent of a scattering region is small at the lower velocities (-1700 km s-1 ≤ v ≤ 0 km s-1).
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