Observational signatures of feedback in QSO absorption spectra

TL;DR

This paper explores how feedback from galaxy formation and active galactic nuclei impacts the intergalactic medium, affecting quasar absorption spectra and providing observable signatures of such feedback processes.

Contribution

It introduces observational methods to detect feedback effects in the intergalactic medium via quasar absorption lines, linking feedback to specific spectral features.

Findings

Feedback reduces absorption in the Lyman alpha forest at high redshift.

Galactic winds influence the number and properties of high-column-density absorption lines.

Multiple sight-lines and higher-order Lyman lines can probe feedback effects.

Abstract

Models for the formation of galaxies and clusters of galaxies require strong feedback in order to explain the observed properties of these systems. We investigate whether such feedback has observational consequences for the intergalactic medium, as probed in absorption towards background quasars. A typical quasar sight-line intersects one proto-cluster per unit redshift, and significant feedback from forming galaxies or AGN, heating the proto-cluster gas, will result in a large clearing of reduced absorption in the Lyman alpha-forest. Such a gap could be detected at redshift > 3 when the mean opacity is high. Feedback from Lyman-break galaxies in proto-clusters can be probed by the absorption lines produced in their winds. Strong feedback from galaxies has a major impact on the number and properties of absorption lines with neutral hydrogen column densities of 10^16/ cm^2. This feedback can be probed with multiple sight-lines and by studying the unsaturated higher-order lines of the Lyman series. Galactic winds from dwarf galaxies should break-up into clouds, in order not to over produce the number of absorption lines. These clouds can then coast to large distances.