Méthodes d'analyse et Propriétés Physiques des Sytèmes Absorbants dans le Spectre des Quasars

Content Provider	Semantic Scholar
Author	Aracil, Bastien
Copyright Year	2004
Abstract	Results are presented for our search for warm-hot gas towards the quasar Q 0329−385. We identify ten O vi systems of which two are within 5000 km s−1 of zem and a third one should be of intrinsic origin. The seven remaining systems have H i column densities 1013.7≤N(H i)≤1015.6 cm−2. At least ∼1/3 of the individual O vi sub-systems have temperatures T<1×105 K and cannot originate in collisionally ionized gas. Photoionization by a hard UV background field reproduces well the ionic ratios for metallicities in the range 10−2.5-10−0.5 solar, with possibly sub-solar N/C relative abundance. For [O/C]=0, the sizes inferred for the O vi clouds are in some cases larger than the maximum extent implied by the Hubble flow. This constraint is fulfilled assuming a moderate overabundance of oxygen relative to carbon. For a soft UV ionizing spectrum, an overabundance of O/C is required, [O/C]≈0.0-1.3. For a hard(soft) UV spectrum and [O/C]=0(1), the O vi regions have overdensities ρ/ρ≈10-40. keywords:cosmology: observations – intergalactic medium – galaxies: halos – quasars: absorption lines
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Language	English
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Resource Type	Article