X-Ray Investigation of Possible Super-Eddington Accretion in a Radio-loud Quasar at <i>z</i> = 6.13
Bibliographic record
Abstract
Abstract We present radio and X-ray observations of the recently discovered z = 6.13 radio-powerful quasar RACS J032021.44−352104.1 using the upgraded Giant Metrewave Radio Telescope, the Australia Telescope Compact Array, the Australian Large Baseline Array, and Chandra. The observed radio properties are in line with what is typically observed in high-z radio quasars (α r = 0.72 ± 0.02 and L 1.4 GHz = 5.8 ± 0.9 × 1026 W Hz−1). Despite the relatively low X-ray flux observed, F 0.5−7.0 keV = 2.3 ± 0.5 × 10−14 erg s−1 cm−2, the intrinsic luminosity in the 2–10 keV rest frame is markedly high, L 2 - 10 keV = 1 . 8 − 0.7 + 1.1 × 1 0 46 erg s−1, making RACS J032021.44−352104.1 one of the most luminous quasars currently known at z > 5.5. The high X-ray luminosity is largely driven by an extrapolation to energies below the observable X-ray window with Chandra and the slope derived in the 0.5–7 keV band (or 3.5–50 keV in the rest frame; ΓX = 3.3 ± 0.4). By analyzing the overall spectral energy distribution of the quasar, we found that the remarkably soft X-ray emission (1) cannot be produced by relativistic jets, even when relativistic boosting is considered, and (2) is consistent with expectations for a super-Eddington accreting supermassive black hole. If such a high accretion rate was confirmed, this source would be a unique laboratory to study high accretion in the early Universe and could help resolve some challenges inherent in early black hole growth paradigms.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".