Anisotropic Active Galactic Nucleus Outflows and Enrichment of the Intergalactic Medium. I. Metal Distribution
Abstract
We investigate the cosmological-scale influence of outflows driven by active galactic nuclei (AGNs) on metal enrichment of the intergalactic medium (IGM). AGNs are located in dense cosmological structures which tend to be anisotropic. We designed a semianalytical model for anisotropic AGN outflows which expand away along the direction of least resistance. This model was implemented into a cosmological numerical simulation algorithm for simulating the growth of large-scale structure in the universe. Using this modified algorithm, we perform a series of nine simulations inside cosmological volumes of size (128 h -1 Mpc)3, in a concordance ΛCDM universe, varying the opening angle of the outflows, the lifetimes of the AGNs, their kinetic fractions, and their level of clustering. For each simulation, we compute the volume fraction of the IGM enriched in metals by the outflows. The resulting enriched volume fractions are relatively small at z gsim 2.5, and then grow rapidly afterward up to z = 0. We find that AGN outflows enrich from 65% to 100% of the entire universe at the present epoch, for different values of the model parameters. The enriched volume fraction depends weakly on the opening angle of the outflows. However, increasingly anisotropic outflows preferentially enrich underdense regions, a trend found more prominent at higher redshifts and decreasing at lower redshifts. The enriched volume fraction increases with increasing kinetic fraction and decreasing AGN lifetime, and level of clustering.
- Publication:
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The Astrophysical Journal
- Pub Date:
- October 2009
- DOI:
- 10.1088/0004-637X/704/2/1002
- arXiv:
- arXiv:0905.3560
- Bibcode:
- 2009ApJ...704.1002G
- Keywords:
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- cosmology: theory;
- galaxies: active;
- intergalactic medium;
- methods: N-body simulations;
- quasars: general;
- Astrophysics - Cosmology and Extragalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 19 pages, 16 figures, submitted. The version uploaded here does not contain Figs 5, 6 &