SIMBAD references

We investigate the large-scale influence of outflows from active galactic nuclei (AGNs) in enriching the intergalactic medium (IGM) with metals in a cosmological context. We combine cosmological simulations of large-scale structure formation with a detailed model of metal enrichment, in which outflows expand anisotropically along the direction of least resistance, distributing metals into the IGM. The metals carried by the outflows are generated by two separate stellar populations: stars located near the central AGN, and stars located in the greater galaxy. Using this algorithm, we performed a series of five simulations of the propagation of AGN-driven outflows in a cosmological volume of size (128 h^–1 Mpc)³ in a ΛCDM universe, and analyze the resulting metal enrichment of the IGM. We found that the metallicity induced in the IGM is greatly dominated by AGNs having bolometric luminosity L>10⁹ L_☉, sources with 10⁸ < L/L_☉< 10⁹ having a negligible contribution. Our simulations produced an average IGM metallicity of [O/H] = -5 at z = 5.5, which then rises gradually, and remains relatively flat at a value [O/H] = -2.8 between z = 2 and z = 0. The ejection of metals from AGN host galaxies by AGN-driven outflows is found to enrich the IGM to >10%-20% of the observed values, the number dependent on redshift. The enriched IGM volume fractions are small at z>3, then rise rapidly to the following values at z = 0: 6%-10% of the volume enriched to [O/H]> - 2.5, 14%-24% volume to [O/H]> - 3, and 34%-45% volume to [O/H]> - 4. At z ≥ 2, there is a gradient of the induced enrichment, the metallicity decreasing with increasing IGM density, enriching the underdense IGM to higher metallicities, a trend more prominent with increasing anisotropy of the outflows. This can explain observations of the metal-enriched low-density IGM at z ∼ 3-4.