Details

Autor(en) / Beteiligte

• D'Odorico, V.
• Cupani, G.
• Cristiani, S.
• Maiolino, R.
• Molaro, P.
• Nonino, M.
• Centurión, M.
• Cimatti, A.
• di Serego Alighieri, S.
• Fiore, F.
• Fontana, A.
• Gallerani, S.
• Giallongo, E.
• Mannucci, F.
• Marconi, A.
• Pentericci, L.
• Viel, M.
• Vladilo, G.

Titel

Metals in the IGM approaching the re-ionization epoch: results from X-shooter at the VLT

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2013-10, Vol.435 (2), p.1198-1232

Ort / Verlag

London: Oxford University Press

Erscheinungsjahr

2013

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We present the results of observations taken with the X-shooter spectrograph devoted to the study of quasars at z ∼ 6. This paper focuses on the properties of metals at high redshift traced, in particular, by the C iv doublet absorption systems. Six objects were observed with resolutions 27 and 34 km s−1 in the visual, and 37.5 and 53.5 km s−1 in the near-infrared. We detected 102 C iv lines in the range: 4.35 < z < 6.2 of which 27 are above z ∼ 5. Thanks to the characteristics of resolution and spectral coverage of X-shooter, we could also detect 25 Si iv doublets associated with the C iv at z 5. The column density distribution function of the C iv line sample is observed to evolve in redshift for z 5.3, with respect to the normalization defined by low-redshift (1.5 < z < 4) C iv lines. This behaviour is reflected in the redshift evolution of the C iv cosmic mass density, , of lines with column density in the range , which is consistent with a drop of a factor of ∼2 for z 5.3. Considering only the stronger C iv lines ( ), gently rises by a factor of ∼10 between z 6.2 and z 1.5 with a possible flattening towards z ∼ 0. The increase is well fitted by a power law: . An insight into the properties of the C iv absorbers and their evolution with redshift is obtained by comparing the observed column densities of associated C iv, Si iv and C ii absorptions with the output of a set of cloudy photoionization models. As already claimed by cosmological simulations, we find that C iv is a good tracer of the metallicity in the low-density intergalactic medium (IGM) gas at z ∼ 5-6 while at z ∼ 3 it arises in gas with overdensity δ ∼ 100.