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Detectability of cold streams into high-zz galaxies by absorption lines

2012
4 pages
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  • Published: 2012
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Abstract: (Grobid)
Cold gas streaming along the dark-matter filaments of the cosmic web is predicted to be the major source of fuel for disc buildup, violent disk instability and star formation in massive galaxies at high redshift. I investigate to what extent such cold gas is detectable in the extended circum- galactic environment of galaxies via selected low ionisation metal absorp­tion lines. I model the expected absorption signatures using high resolution zoom-in AMR cosmological simulations. In the postprocessing, I distinguish between self- shielded gas and unshielded gas. In the self-shielded gas, which is optically thick to Lyman continuum radia­tion, I assume pure collisional ionisation for species with an ionisation potential greater than 13.6 eV. In the optically thin, unshielded gas these species are also photoionised by the meta­ galactic radiation. I compute the absorption line profiles of radiation emitted by the galaxy at the centre of the same halo. I predict the strength of the absorption signal for individual galaxies without stacking. I find that the absorption profiles produced by the streams are consistent with observations of absorption and emission profiles in high redshift galaxies. Due to the low metallicities in the streams, and their low covering factors, the metal absorption features are weak and difficult to detect.