Metals in the z~3 intergalactic medium: results from an ultra-high signal-to-noise ratio UVES quasar spectrum

Abstract

In this work, we investigate the abundance and distribution of metals in the intergalactic medium (IGM) at $⟨z⟩\simeq 2.8$ through the analysis of an ultra-high signal-to-noise ratio UVES spectrum of the quasar HE0940-1050. In the CIV forest, our deep spectrum is sensitive at $3\sigma$ to lines with column density down to $\log N_{\mathrm{CIV}}\simeq 11.4$ and in 60 per cent of the considered redshift range down to $\simeq 11.1$. In our sample, all HI lines with $\log N_{\mathrm{HI}}\ge 14.8$ show an associated CIV absorption. In the range $14.0\le \log N_{\mathrm{HI}}<14.8$, 43 per cent of HI lines has an associated CIV absorption. At $\log N_{\mathrm{HI}}<14.0$, the detection rates drop to $<10$ per cent, possibly due to our sensitivity limits and not to an actual variation of the gas abundance properties. In the range $\log N_{\mathrm{HI}}\ge 14$, we observe a fraction of HI lines with detected CIV a factor of 2 larger than the fraction of HI lines lying in the circum-galactic medium (CGM) of relatively bright Lyman-break galaxies hosted by dark matter haloes with $⟨M⟩\sim 10^{12}$ M${}_{\odot }$. The comparison of our results with the output of a grid of photoionization models and of two cosmological simulations implies that the volume filling factor of the IGM gas enriched to a metallicity $\log Z/Z_{\odot }\ge -3$ should be of the order of $\sim 10-13$ percent. In conclusion, our results favour a scenario in which metals are found also outside the CGM of bright star-forming galaxies, possibly due to pollution by lower mass objects and/or to an early enrichment by the first sources.

23 pages, 28 figures. Accepted by MNRAS on 2016 August 24. Received 2016 August 10; in original form 2016 April 15

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Cited by in corpus (7)

• The Cosmic Baryon and Metal Cycles
• Exploring the Thermal State of the Low-Density Intergalactic Medium at z=3 with an Ultra-High Signal-to-Noise QSO Spectrum
• The spectroscopic follow-up of the QUBRICS bright quasar survey
• Simulating MOS science on the ELT: Ly$\alpha$ forest tomography
• Simulated metal and HI absorption lines at the conclusion of Reionization
• Theoretical study of an LAE-CIV absorption pair at z = 5.7
• Detecting neutral hydrogen at z > 3 in large spectroscopic surveys of quasars