Circum-galactic medium in the halo of quasars

TL;DR

This study investigates the distribution and properties of circum-galactic gas around quasars at z~1 using absorption lines, revealing patchy gas structures and their relation to galaxy environments.

Contribution

It provides new observational insights into the extent, patchiness, and environmental dependence of circum-galactic gas in quasar host halos.

Findings

Absorption systems detected up to 200 kpc from quasars.

Gas distribution is patchy with decreasing covering fraction beyond 100 kpc.

Relations between circum-galactic medium properties and galaxy environments are explored.

Abstract

The properties of circum-galactic gas in the halo of quasar host galaxies are investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along the line of sight close to quasars. We used optical spectroscopy of closely aligned pairs of quasars (projected distance $\leq$ 200 kpc, but at very different redshift) obtained at the VLT and Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of quasars at z$\sim$1. Absorption systems of EW $\geq$ 0.3 $\rm{\AA}$ associated with the foreground quasars are revealed up to 200 kpc from the centre of the host galaxy, showing that the structure of the absorbing gas is patchy with a covering fraction quickly decreasing beyond 100 kpc. In this contribution we use optical and near-IR images obtained at VLT to investigate the relations between the properties of the circum-galactic medium of the host galaxies and of the large scale galaxy environments of the foreground quasars.