The quiet intracluster medium in the core of the Perseus Cluster
Bibliographic record
Abstract
The Quiet Intracluster Medium in the Core of the Perseus Cluster The Hitomi collaboration Clusters of galaxies are the most massive gravitationally-bound objects in the Universe and are still forming.They are thus important probes 1 of cosmological parameters and a host of astrophysical processes.Knowledge of the dynamics of the pervasive hot gas, which dominates in mass over stars in a cluster, is a crucial missing ingredient.It can enable new insights into mechanical energy injection by the central supermassive black hole and the use of hydrostatic equilibrium for the determination of cluster masses.X-rays from the core of the Perseus cluster are emitted by the 50 million K diffuse hot plasma filling its gravitational potential well.The Active Galactic Nucleus of the central galaxy NGC1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma.These likely induce motions in the intracluster medium and heat the inner gas preventing runaway radiative cooling; a process known as Active Galactic Nucleus Feedback 2-6 .Here we report on Hitomi X-ray observations of the Perseus cluster core, which reveal a remarkably quiescent atmosphere where the gas has a line-of-sight velocity dispersion of 164±10 km/s in a region 30-60 kpc from the central nucleus.A gradient in the line-of-sight velocity of 150±70 km/s is found across the 60 kpc image of the cluster core.Turbulent pressure support in the gas is 4% or less of the thermodynamic pressure, with large scale shear at most doubling that estimate.We infer that total cluster masses determined from hydrostatic equilibrium in the central regions need little correction for turbulent pressure.The JAXA Hitomi X-ray Observatory 7 was launched on 2016 February 17 from Tanegashima, Japan.It carries the non-dispersive Soft X-ray Spectrometer SXS 8 , which is a calorimeter cooled to 0.05K giving 4.9 eV FWHM (E/dE=1250 at 6 keV) Gaussian-shaped energy response over a 6 x 6 pixel array (total 3 x 3 arcmin).It operates over an energy range of 0.3-12 keV with X-rays focused by a mirror 9 with angular resolution of 1.2 arcmin (HPD).A gate valve was in place for early observations to minimize the risk of contamination from outgassing of the spacecraft.It includes a Be window that absorbs most X-rays below ~3 keV.The SXS can detect bulk and turbulent motions of the intracluster medium (ICM) by measuring We acknowledge all the JAXA members who have contributed to the ASTRO-H (Hitomi) project.All U.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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".