Bosman, SEI; Becker, GD; Haehnelt, MG; Hewett, PC; McMahon, RG; Mortlock, DJ; Simpson, C; Bosman, SEI; Becker, GD; Haehnelt, MG; Hewett, PC; McMahon, RG; Mortlock, DJ; Simpson, C; Venemans, BP; - view fewer (2017) A deep search for metals near redshift 7: the line of sight towards ULAS J1120+0641. Monthly Notices of the Royal Astronomical Society , 470 (2) pp. 1919-1934. 10.1093/mnras/stx1305.

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Abstract

We present a search for metal absorption line systems at the highest redshifts to date using a deep (30 h) Very Large Telescope/X-Shooter spectrum of the z = 7.084 quasi-stellar object (QSO) ULAS J1120+0641. We detect seven intervening systems at z > 5.5, with the highest redshift system being a C IV absorber at z = 6.51. We find tentative evidence that the mass density of C IV remains flat or declines with redshift at z < 6, while the number density of C II systems remains relatively flat over 5 < z < 7. These trends are broadly consistent with models of chemical enrichment by star formation-driven winds that include a softening of the ultraviolet background towards higher redshifts. We find a larger number of weak (Wrest < 0.3 Å) Mg II systems over 5.9 < z < 7.0 than predicted by a power-law fit to the number density of stronger systems. This is consistent with trends in the number density of weak Mg II systems at z ≲ 2.5, and suggests that the mechanisms that create these absorbers are already in place at z ∼ 7. Finally, we investigate the associated narrow Si IV, C IV and N V absorbers located near the QSO redshift, and find that at least one component shows evidence of partial covering of the continuum source.

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