Determining the Locations of Dust Sources in FeLoBAL Quasars

TL;DR

This study investigates the locations of dust sources in FeLoBAL quasars by analyzing spectroscopic data, revealing that reddening likely occurs at larger distances from the nucleus than the narrow line regions.

Contribution

It provides new insights into the dust distribution and reddening sources in FeLoBAL quasars through spectroscopic analysis of SDSS data.

Findings

Approximately 23% of Mg II BALs show strong Balmer emission.

Significant reddening (E(B-V) ≥ 0.1) observed in about 23% of Mg II BALs.

Reddening sources are likely located beyond the narrow line regions.

Abstract

We conduct a spectroscopic search of quasars observed by the Sloan Digital Sky Survey (SDSS) with broad absorption line (BAL) troughs due to Mg II and troughs due to Fe II that simultaneously exhibit strong Balmer narrow emission lines (NELs). We find that in a redshift range of 0.4 less than or equal to z less than or equal to 0.9 approximately 23 of the 70 Mg II BALs and 4 of a subset of 15 Fe II BALs exhibit strong Balmer emission. We also find significant fractions of Mg II BALs (approximately 23%) and those Mg II BALs with Fe II troughs (approximately 27%) have strong continuum reddening, E(B - V) greater than or equal to 0.1. From measurements of the Balmer decrement in three objects, we find similarly significant reddening of the NEL region in three of the four objects; the NELs in the fourth object are not measurable. We also include one object in this study not taken from the SDSS sample that shows Fe II absorption and strong narrow emission, but due to measurement uncertainty and low continuum reddening the comparison is consistent but inconclusive. We find a trend in both the Mg II and Fe II BAL samples between the NEL reddening and continuum reddening. Because the narrow line reddening is consistent with the continuum reddening in every object in the two SDSS samples, it suggests that the reddening sources in these objects likely exist at larger radial distances than the narrow line regions from the central nucleus.