Outflows and the Physical Properties of Quasars

TL;DR

This study analyzes a large quasar sample to understand how broad absorption line properties relate to black hole mass, luminosity, and spectral features, revealing that outflow velocities are driven by ultraviolet luminosity and spectral slope.

Contribution

It provides new insights into how quasar outflow velocities and BAL occurrence depend on physical properties like luminosity and spectral slope, emphasizing the role of ultraviolet line scattering.

Findings

BALs are more common in high Eddington ratio quasars.

Higher bolometric luminosity correlates with increased BAL presence.

Maximum outflow velocities increase with luminosity and blueness of spectral slope.

Abstract

We have investigated a sample of 5088 quasars from the Sloan Digital Sky Survey Second Data Release in order to determine how the frequency and properties of broad absorptions lines (BALs) depend on black hole mass, bolometric luminosity, Eddington fraction (L/L_Edd), and spectral slope. We focus only on high-ionization BALs and find a number of significant results. While quasars accreting near the Eddington limit are more likely to show BALs than lower $L/L_{Edd}$ systems, BALs are present in quasars accreting at only a few percent Eddington. We find a stronger effect with bolometric luminosity, such that the most luminous quasars are more likely to show BALs. There is an additional effect, previously known, that BAL quasars are redder on average than unabsorbed quasars. The strongest effects involving the quasar physical properties and BAL properties are related to terminal outflow velocity. Maximum observed outflow velocities increase with both the bolometric luminosity and the blueness of the spectral slope, suggesting that the ultraviolet luminosity to a great extent determines the acceleration. These results support the idea of outflow acceleration via ultraviolet line scattering.