The metallicity distribution of H i systems in the EAGLE cosmological simulations. Issue 4 (7th March 2018)

• Record Type: Journal Article
• Authors: Rahmati, Alireza; Oppenheimer, Benjamin D
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 476:Issue 4(2018)
• Page Start: 4865
• Page End: 4871
• Publication Date: 2018-03-07
• Subjects: methods: numerical -- galaxies: evolution -- galaxies: formation -- intergalactic medium -- quasars: absorption lines -- cosmology: theory; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty610
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: The metallicity of strong $\mathrm{H}\, \small {I}$ systems, spanning from damped Lyman α absorbers (DLAs) to Lyman-limit systems (LLSs), is explored between z = 5 → 0 using the EAGLE high-resolution cosmological hydrodynamic simulation of galaxy formation. The metallicities of LLSs and DLAs steadily increase with time in agreement with observations. DLAs are more metal rich than LLSs, although the metallicities in the LLS column density range ($N_{\mathrm{H}\, \small {I} }\approx 10^{17}\hbox{--}10^{20} \, {\rm cm^{-2}}$ ) are relatively flat, evolving from a median $\mathrm{H}\, \small {I}$ -weighted metallicity of ${Z}\lesssim 10^{-2}\, {\rm Z}_{{\odot }}$ at z = 3 to ≈10 −0.5 Z⊙ by z = 0. The metal content of $\mathrm{H}\, \small {I}$ systems tracks the increasing stellar content of the Universe, holding $\approx\! 5\, \, \rm{per\, \, cent}$ of the integrated total metals released from stars at z = 0. We also consider partial LLS (pLLS, $N_{\mathrm{H}\, \small {I} }\approx 10^{16}\hbox{--}10^{17} \, {\rm cm^{-2}}$ ) metallicities, and find good agreement with Wotta et al. for the fraction of systems above (37 per cent) and below (63 per cent) 0.1 Z⊙ . We also find a large dispersion of pLLS metallicities, although we do not reproduce the observed metallicity bimodality and instead we make the prediction that a larger sample will yield more pLLSs around 0.1 Z⊙ . We underpredict the median metallicity of strong LLSs, and predict a population of Z < 10 −3 Z⊙ DLAs at z > 3 that are not observed, which may indicate more widespread early enrichment in the real Universe compared to EAGLE.