Narrow-absorption Line Complex. IV. Line-driven Radiative Outflows in Broad-absorption Line Quasars

Abstract

Abstract It has been reported that some broad-absorption lines (BALs) in quasar spectra can be decomposed into multiple narrow-absorption lines (NALs), which we define as “Type N BALs.” In this paper, using the spectra of 2005 BAL quasars from the Sloan Digital Sky Survey (SDSS), we have visually identified a total of 6764 C iv λλ1548 and 1551 NAL systems with 1.4186 ≤ z abs ≤ 3.8005, including 4174 C iv NAL systems within BAL troughs from 1349 quasars and 2590 outside BAL troughs from 1319 quasars. About two-thirds of the BAL quasars in the total sample contain Type N BALs, indicating the ubiquity of Type N BALs, which serve as a new perspective for studying outflows in the context of the NAL complex. Moreover, we find that, for both samples of C iv NAL systems within and outside BAL troughs, the distributions of velocity separation among distinct C iv NAL systems in the same quasar show significant excesses at the positions of C iv and Si iv doublet splittings, which offers statistical evidence for the idea that radiative forces play a significant role in driving both BAL and NAL outflows in BAL quasars.