Circum-Galactic Medium in the Halo of Quasars

Riccardo Ottolina,Michela Uslenghi,Renato Falomo,Aldo Treves,Emanuele Paolo Farina,Riccardo Scarpa,Jari K Kotilainen

doi:10.3389/fspas.2017.00061

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.

Highlights

The standard model for the origin of the extreme luminosity of quasars considers that a supermassive black hole shines as a quasar when intense mass inflow takes place, possibly as a consequence of tidal forces in dissipative events (e.g., Di Matteo et al, 2005)
The circum-galactic medium of quasar host galaxies is expected to be populated by streams, cool gas clouds and tidal debris, as commonly observed in interacting galaxies (e.g., Sulentic et al, 2001; Cortese et al, 2006)
One of the effective ways to study the circum-galactic medium of galaxies at high redshift is to investigate the absorption features that they imprint in the spectra of quasars

Summary

INTRODUCTION

The standard model for the origin of the extreme luminosity of quasars considers that a supermassive black hole shines as a quasar when intense mass inflow takes place, possibly as a consequence of tidal forces in dissipative events (e.g., Di Matteo et al, 2005). Projected quasar pairs (Figure 1 left) are ideal observational tools for this purpose, since the light of the very bright source in the background (z ≡ zB) goes through the extended halo of the foreground (z ≡ zF < zB) object (e.g., Hennawi et al, 2006; Farina et al, 2013). This can be evidenced by absorption lines at the foreground redshift: an example is reported in Figure 1 right. In this paper we analyze optical and NIR images of foreground quasars in order to investigated their closed environments and their host galaxies

SAMPLE AND OBSERVATIONS

ANALYSIS

PRELIMINARY RESULTS