We investigate the large-scale influence of outflows from AGNs in enriching the 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 5 simulations of the propagation of AGN-driven outflows in a cosmological volume of size ( 128 h ^ { -1 } { Mpc } ) ^ { 3 } in a \Lambda CDM 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 > 10 ^ { 9 } L _ { \odot } , sources with 10 ^ { 8 } < L / L _ { \odot } < 10 ^ { 9 } having a negligible contribution .
Our simulations produced an average IGM metallicity of \left [ { O } / { H } \right ] = -5 at z = 5.5 , which then rises gradually , and remains relatively flat at a value \left [ { O } / { H } \right ] = -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 \left [ { O } / { H } \right ] > -2.5 , 14 - 24 \% volume to \left [ { O } / { H } \right ] > -3 , and 34 - 45 \% volume to \left [ { O } / { H } \right ] > -4 .
At z \geq 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 metal-enriched low-density IGM at z \sim 3 - 4 .