Simulating the γ-ray emission from galaxy clusters: a universal cosmic ray spectrum and spatial distribution
Bibliographic record
Abstract
Entering a new era of high-energy γ-ray experiments, there is an exciting quest for the first detection of γ-ray emission from clusters of galaxies. To complement these observational efforts, we use high-resolution simulations of a broad sample of galaxy clusters, and follow self-consistent cosmic ray (CR) physics using an improved spectral description. We study CR proton spectra as well as the different contributions of the pion decay and inverse-Compton emission to the total flux and present spectral index maps. We find a universal spectrum of the CR component in clusters with surprisingly little scatter across our cluster sample. When CR diffusion is neglected, the spatial CR distribution also shows approximate universality; it depends however on the cluster mass. This enables us to derive a semi-analytic model for both the distribution of CRs as well as the pion decay γ-ray emission and the secondary radio emission that results from hadronic CR interactions with ambient gas protons. In addition, we provide an analytic framework for the inverse-Compton emission that is produced by shock-accelerated CR electrons and is valid in the full γ-ray energy range. Combining the complete sample of the brightest X-ray clusters observed by ROSAT with our γ-ray scaling relations, we identify the brightest clusters for the γ-ray space telescope Fermi and current imaging air Čerenkov telescopes (IACTs) (MAGIC, HESS, VERITAS). We reproduce the previous result of Pfrommer, but provide somewhat more conservative predictions for the fluxes in the energy regimes of Fermi and IACTs when accounting for the bias of ‘artificial galaxies’ in cosmological simulations. We find that it will be challenging to detect cluster γ-ray emission with Fermi after the second year but this mission has the potential of constraining interesting values of the shock acceleration efficiency after several years of surveying. Comparing the predicted emission from our semi-analytic model to that obtained by means of our scaling relations, we find that the γ-ray scaling relations underpredict, by up to an order of magnitude, the flux from cool-core clusters.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".