Search for intrinsic NALs in BAL/mini-BAL quasar spectra

TL;DR

This study investigates the presence and distribution of intrinsic narrow absorption lines (NALs) in BAL/mini-BAL quasar spectra to understand their relation to quasar geometry and the origin of different absorption features.

Contribution

It provides the first observational evidence that intrinsic NALs are common across quasars regardless of inclination angle, challenging simple geometric models.

Findings

Intrinsic NALs are present in at least 33% of BAL/mini-BAL quasars.

Intrinsic NALs can be located at large distances, exceeding 130 kpc from the quasar.

The distribution of intrinsic NALs suggests complex origins and geometries.

Abstract

Some fraction of narrow absorption lines are physically associated to the quasar/host-galaxy materials (i.e., intrinsic NALs) like those of BALs and mini-BALs. The relation between these three types of absorption lines has not been understood yet, however one interpretation is that these absorption features correspond to different inclination angles. In this study, we search for intrinsic NALs in 11 BAL/mini-BAL quasar spectra retrieved from VLT/UVES public archive, in order to test a possible relation of intrinsic NALs and BALs/mini-BALs in the geometry models. We use partial coverage analysis to separate intrinsic NALs from ones which are associated to cosmologically intervening materials like foreground galaxies and intergalactic medium (i.e., intervening NALs). We identify one reliable and two possible intrinsic NAL systems out of 36 NAL systems in 9 BAL/mini-BAL quasar spectra after removing two quasars without clear BAL features. In spite of a small sample size, we placed a lower limit on the fraction of BAL/mini-BAL quasars that have at least one intrinsic C IV NAL ($\sim33^{+33}_{-18}\%$). This can be interpreted that intrinsic NAL absorbers exist everywhere regardless of inclination angle. We found that one of the intrinsic NAL systems detected in SDSS J121549.80-003432.1 is located at a large radial distance of R > 130 kpc, using a method of photoionization model with ground/excited-state lines. Considering the wide range of intrinsic NAL absorber distribution in inclination angles and radial distances, it suggests that origins and geometry of them are more complicated than we expected.