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ABSTRACT Intervening metal absorption lines in the spectra of z ≳ 6 quasars are fundamental probes of the ionization state and chemical composition of circumgalactic and intergalactic gas near the end of the reionization epoch. Large absorber samples are required to robustly measure typical absorber properties and to refine models of the synthesis, transport, and ionization of metals in the early Universe. The Ultimate XSHOOTER legacy survey of quasars at z ∼ 5.8–6.6 (XQR-30) has obtained high signal-to-noise spectra of 30 luminous quasars, nearly quadrupling the existing sample of 12 high quality z ∼ 6 quasar spectra. We use this unprecedented sample to construct a catalogue of 778 systems showing absorption in one or more of Mg ii (360 systems), Fe ii (184), C ii (46), C iv (479), Si iv (127), and N v (13) which span 2 ≲ z ≲ 6.5. This catalogue significantly expands on existing samples of z ≳ 5 absorbers, especially for C iv and Si iv which are important probes of the ionizing photon background at high redshift. The sample is 50 per cent (90 per cent) complete for rest-frame equivalent widths W ≳ 0.03 Å (0.09 Å). We publicly release the absorber catalogue along with completeness statistics and a python script to compute the absorption search path for different ions and redshift ranges. This data set is a key legacy resource for studies of enriched gas from the era of galaxy assembly to cosmic noon, and paves the way for even higher redshift studies with JWST and 30 m-class telescopes.
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The evolution of the Si iv content in the Universe from the epoch of reionization to cosmic noon
ABSTRACT We investigate the abundance and distribution of metals in the high-redshift intergalactic medium and circum-galactic medium through the analysis of a sample of almost 600 Si iv absorption lines detected in high- and intermediate-resolution spectra of 147 quasars. The evolution of the number density of Si iv lines, the column density distribution function, and the cosmic mass density are studied in the redshift interval 1.7 ≲ z ≲ 6.2 and for log N(Si iv) ≥ 12.5. All quantities show a rapid increase between z ∼ 6 and z ≲ 5 and then an almost constant behaviour to z ∼ 2 in very good agreement with what is already observed for C iv absorption lines. The present results are challenging for numerical simulations: When simulations reproduce our Si iv results, they tend to underpredict the properties of C iv, and when the properties of C iv are reproduced, the number of strong Si iv lines [log N(Si iv) > 14] is overpredicted.
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- PAR ID:
- 10364669
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 512
- Issue:
- 2
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 2389-2401
- Size(s):
- p. 2389-2401
- Sponsoring Org:
- National Science Foundation
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