13 - Large-scale expansion of AGN outflows in a cosmological volume

Summary

Introduction

Outflows from AGN are observed in a wide variety of forms: radio galaxies, broad absorption line quasars, Seyfert galaxies exhibiting intrinsic absorption in the UV, broad emission lines, warm absorbers and absorption lines in X-rays (e.g. Creenshaw et al. 2003; Everett 2007). There have been studies on the cosmological impact of quasar outflows on large scales (Furlanetto & Loeb 2001, here after FL01; Scannapieco and Oh 2004, hereafter SO04; Levine & Gnedin 2005, hereafter LG05). Barai (2008) investigated the cosmological influence of radio galaxies over the Hubble time. All these studies considered spherically expanding outflows.

On cosmological scales an outflow is expected to move away from the highdensity regions of large-scale structures, with the outflowing matter getting channelled into low-density regions of the universe (Martel and Shapiro 2001). We implement such anisotropic AGN outflows within a cosmological volume. The simulation methodology is given in Section 13.2, and the results are discussed in Section 13.3.

The numerical setup

N-body simulation and distribution

We simulate the growth of large-scale structures in a cubic cosmological volume of comoving size L_box = 128h⁻¹ Mpc. We use the particle-mesh (PM) algorithm, with 256³ equal-mass particles, on a 512³ grid. A particle has a mass of 1.32 × 10¹⁰M_⊙, and the grid spacing is Δ = 0.25h⁻¹ Mpc. We consider a concordance ∧CDM model with the cosmological parameters:Ω_M = 0.268, Ω_∧ = 0.732, H₀ = 70.4 km s⁻¹ Mpc⁻¹, Ω_b = 0.0441, n_s = 0.947, and T_CMB = 2.725.