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 in the visual, and 37.5 and 53.5 km/s 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, Omega_CIV, of lines with column density in the range 13.4 < log N(C IV) < 15, which is consistent with a drop of a factor of ~2 for z>~ 5.3. Considering only the stronger C IV lines (13.8 < log N(CIV) < 15), Omega_CIV gently rises by a factor of ~10 between z ~ 6.2 and z~ 1.5 with a possible flattening toward z ~ 0. The increase is well fitted by a power law: Omega_CIV = (2+-1)x10^-8 [(1+z)/4]^-3.1+-0.1. 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 photo-ionization models. As already claimed by cosmological simulations, we find that C IV is a good tracer of the metallicity in the low-density intergalacitc medium gas at z ~ 5-6 while at z ~ 3 it arises in gas with over density delta ~100.

Metals in the IGM approaching the re-ionization epoch: results from X-shooter at the VLT / 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.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 435:2(2013), pp. 1198-1232. [10.1093/mnras/stt1365]

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

Viel, M.;
2013-01-01

Abstract

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 in the visual, and 37.5 and 53.5 km/s 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, Omega_CIV, of lines with column density in the range 13.4 < log N(C IV) < 15, which is consistent with a drop of a factor of ~2 for z>~ 5.3. Considering only the stronger C IV lines (13.8 < log N(CIV) < 15), Omega_CIV gently rises by a factor of ~10 between z ~ 6.2 and z~ 1.5 with a possible flattening toward z ~ 0. The increase is well fitted by a power law: Omega_CIV = (2+-1)x10^-8 [(1+z)/4]^-3.1+-0.1. 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 photo-ionization models. As already claimed by cosmological simulations, we find that C IV is a good tracer of the metallicity in the low-density intergalacitc medium gas at z ~ 5-6 while at z ~ 3 it arises in gas with over density delta ~100.
2013
435
2
1198
1232
http://arxiv.org/abs/1306.4604v2
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.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11767/16709
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