Unraveling the structure of the stratified ultra-fast outflows in PDS 456 with XRISM
Bibliographic record
Abstract
Abstract Multiple clumpy wind components ($v_\mathrm{out}\sim 0.2\!-\!0.3c$) in the luminous quasar PDS 456 have recently been resolved in the Fe K band for the first time, thanks to the high-resolution X-ray spectrometer Resolve onboard XRISM. In this paper, we investigate the structure of ultra-fast outflows (UFOs) using coordinated observations from XRISM, XMM–Newton, and NuSTAR, along with the self-consistently calculated photoionization model PION. Our results reveal a stratified ionization structure, characterized by a scaling relation between wind velocity and ionization parameter $v_\mathrm{out}\propto \xi ^{(0.14\pm 0.04)}$. To evaluate the screening effect in photoionization modeling, we tested all possible order permutations of six PION components. We find that highly ionized UFOs ($\log \xi >4.5$) are insensitive to their relative positions, whereas the soft X-ray UFO ($\log \xi \sim 3$ and $v_\mathrm{out}\sim 0.27c$) and the lowest-ionized hard X-ray UFO ($\log \xi \sim 4.1$ and $v_\mathrm{out}\sim 0.23c$) are statistically favored—based on the evidence from both the C-statistic and Bayesian analysis—to occupy the middle and innermost layers, respectively. This suggests a possible trend where slower UFOs are launched from regions closer to the supermassive black hole. The soft X-ray UFO is found to be thermally unstable, regardless of its relative position. However, its location remains unclear. Our sequence analysis and its similarity to hard X-ray UFOs suggest that they may be co-spatial, while variability constraints support its location within the broad-line region at sub-parsec scales. Simulations with XRISM with an open gate valve show that high-resolution soft X-ray data can enhance the reliability of our results. Furthermore, simulations with the future X-ray mission NewAthena demonstrate its capability to resolve the absorber sequence and spatial distributions, enabling the determination of UFO structures and their roles in active galactic nucleus feedback.
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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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".