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High Redshift Intergalactic C IV Abundance Measurements from the Near-Infrared Spectra of Two z~6 QSOs
Astrophysics · Submitted 30 May 2006
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim The trend of constant $\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift.
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The abstract, sentence by sentence
New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. The trend of constant $\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of $\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. The lack of a decline in $\Omega_{CIV}$ at high redshift may indicate that integrated CIV measurements are sensitive to the instantaneous rate of feedback from galaxy formation at each epoch. Alternatively, it could result from a balance in the evolution of the intergalactic gas density, ionization conditions, and heavy-element abundance over time.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. | contribution 0.90 | 0.97 | 0.04 | asserted 1.00 |
| s1 | These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. | method 0.98 | 0.93 | 0.02 | asserted 0.99 |
| s2 | Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. | method 0.98 | 0.95 | 0.02 | asserted 0.98 |
| s3 | The trend of constant $\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. | result 0.98 | 0.79 | 0.78 | hedged possibility 0.83 |
| s4 | The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. | result 0.87 | 0.66 | 0.09 | hedged possibility 0.99 |
| s5 | The constant value of $\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. | interpretation 1.00 | 0.72 | 0.23 | hedged possibility 0.86 |
| s6 | The lack of a decline in $\Omega_{CIV}$ at high redshift may indicate that integrated CIV measurements are sensitive to the instantaneous rate of feedback from galaxy formation at each epoch. | interpretation 1.00 | 0.59 | 0.11 | hedged possibility 1.00 |
| s7 | Alternatively, it could result from a balance in the evolution of the intergalactic gas density, ionization conditions, and heavy-element abundance over time. | interpretation 1.00 | 0.14 | 0.06 | hedged possibility 0.99 |
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Original abstract
New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. The trend of constant $\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of $\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. The lack of a decline in $\Omega_{CIV}$ at high redshift may indicate that integrated CIV measurements are sensitive to the instantaneous rate of feedback from galaxy formation at each epoch. Alternatively, it could result from a balance in the evolution of the intergalactic gas density, ionization conditions, and heavy-element abundance over time.
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