Quasar Outflows

Research Questions

• What are the locations, energetics, and physical properties of quasar outflows?

• What are the relationships between the different types of outflows (Broad Absorption Lines, Mini-Broad Absorption Lines, and Narrow Absorption Lines)?

• Are the mass loss rates and kinetic energies in quasars sufficient for AGN feedback to occur?

Short Overview

Through geometrical arguments and substantial variability in the spectra, we find that the moving structures of outflows are clouds which are ~ 1 pc from the black hole for both mini-BALs and BALs. We also find that mini-BALs seem to be more variable than BALs. And lastly, using lower limit on total column density for the BAL quasar in the sample, we find that the kinetic energy is at least marginally sufficient for AGN feedback to occur.

Publication

• Moravec et al., HST and ground-based spectroscopy of quasar outflows: from mini-BALs to BALs, 2017, MNRAS, 468, 4539

• An 8 minute video summarizing this work with the public being the intended audience: Cosmic Scrapbook

Summary of Project

Background and Motivation

The observational manifestation of quasar outflows is blue-shifted absorption lines in quasar spectra. There is a wide range of outflow types which are categorized according to their absorption line widths:

• the lines with the smallest width are called Narrow Absorption Line (NALs) and have a width of less than a few hundred km/s (shown in the top of the left panel of the figure below – Hamman+12)

• the most prominent and broadest lines are called Broad Absorption Lines (or BALs) and have widths of greater than or equal to 2000 km/s (shown in the bottom of the left panel of the figure below).

There has been a large effort to understand these two outflow types and thus this study focuses on a class outflow lines with intermediate widths called mini-BALs (shown in the right panel of the figure below – Moravec+17). Of the three classes of absorption lines, mini-BALs, are the least well-understood (as only a few studies with large samples or broad wavelength coverage have been carried out).

Sample and Data

As mini-BALs are the class of absorption lines that are the least well understood, they are the main component of our sample. We created a sample of a variety of outflow strengths ranging from weak mini-BALs to a strong BAL in CIV in order to probe the ranges of physical characteristics of mini-BALs and compare them to BALs. In total we have 6 mini-BALs and one BAL (z~1.6-1.8).

Each quasar has anywhere from 3 to 6 epochs of data taken across a range of approximately 10 years in observers frame and we use this to determine the variability in CIV which can be combined with other measured properties of the outflow lines to characterize the physical structure of the flows. Each quasar was observed once with HST nearly simultaneously with a ground observation - these two observations together give a wide wavelength coverage in the UV that contains important diagnostic lines.