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The FLAMINGO Project: Exploring the X-ray--cosmic-shear cross-correlation as a probe of large-scale structure
Cosmology and Nongalactic Astrophysics · Submitted 2 Feb 2026
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We conclude that to exploit the potential of the X-ray--lensing cross-correlation, it will be necessary to resolve fainter AGN, and to use external constraints to break the degeneracy between baryonic feedback and cosmology.
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The abstract, sentence by sentence
Baryonic feedback processes associated with galaxy formation directly influence the large-scale structure by redistributing gas. Recent measurements of the kinetic Sunyaev-Zel'dovich effect and stacks of X-ray emission from optically selected galaxy clusters suggest that feedback from Active Galactic Nuclei (AGN) is more efficient at expelling gas from low-mass clusters than previously thought. The measurement of the cross-correlation between cosmic shear and diffuse X-ray emission provides a new probe of the distribution of gas in groups and clusters. We use the FLAMINGO cosmological, hydrodynamical simulations to examine the X-ray--cosmic-shear cross-correlation. The cross-correlation is most sensitive to the distribution of gas in haloes with masses $10^{14}\leq M_{200\mathrm{c}}/\mathrm{M}_{\odot}\leq10^{15}$. It is sensitive to the strength of feedback, but the effects of variations in cosmology and baryonic physics are largely degenerate. We compare the FLAMINGO predictions with the cross-correlation between cosmic shear from the Dark Energy Survey and ROSAT all-sky X-ray maps. We find that, if we neglect the X-ray emission from AGN that would remain unresolved by ROSAT, then the fiducial FLAMINGO model is in excellent agreement with the data, while models with stronger or weaker feedback are ruled out. However, if we account for unresolved AGN, either using the direct FLAMINGO predictions or by abundance matching to the observed (extrapolated) AGN luminosity function, then models with stronger feedback are preferred. We conclude that to exploit the potential of the X-ray--lensing cross-correlation, it will be necessary to resolve fainter AGN, and to use external constraints to break the degeneracy between baryonic feedback and cosmology.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Baryonic feedback processes associated with galaxy formation directly influence the large-scale structure by redistributing gas. | background 1.00 | 0.04 | 0.02 | asserted 1.00 |
| s1 | Recent measurements of the kinetic Sunyaev-Zel'dovich effect and stacks of X-ray emission from optically selected galaxy clusters suggest that feedback from Active Galactic Nuclei (AGN) is more efficient at expelling gas from low-mass clusters than previously thought. | background 1.00 | 0.05 | 0.02 | hedged possibility 0.90 |
| s2 | The measurement of the cross-correlation between cosmic shear and diffuse X-ray emission provides a new probe of the distribution of gas in groups and clusters. | background 0.81 | 0.09 | 0.03 | asserted 0.97 |
| s3 | We use the FLAMINGO cosmological, hydrodynamical simulations to examine the X-ray--cosmic-shear cross-correlation. | method 0.84 | 0.95 | 0.02 | asserted 0.95 |
| s4 | The cross-correlation is most sensitive to the distribution of gas in haloes with masses $10^{14}\leq M_{200\mathrm{c}}/\mathrm{M}_{\odot}\leq10^{15}$. | result 0.99 | 0.87 | 0.05 | asserted 1.00 |
| s5 | It is sensitive to the strength of feedback, but the effects of variations in cosmology and baryonic physics are largely degenerate. | result 0.75 | 0.78 | 0.06 | asserted 1.00 |
| s6 | We compare the FLAMINGO predictions with the cross-correlation between cosmic shear from the Dark Energy Survey and ROSAT all-sky X-ray maps. | method 0.88 | 0.92 | 0.02 | asserted 0.95 |
| s7 | We find that, if we neglect the X-ray emission from AGN that would remain unresolved by ROSAT, then the fiducial FLAMINGO model is in excellent agreement with the data, while models with stronger or weaker feedback are ruled out. | result 1.00 | 0.96 | 0.14 | asserted 0.99 |
| s8 | However, if we account for unresolved AGN, either using the direct FLAMINGO predictions or by abundance matching to the observed (extrapolated) AGN luminosity function, then models with stronger feedback are preferred. | result 0.98 | 0.91 | 0.15 | asserted 0.93 |
| s9 | We conclude that to exploit the potential of the X-ray--lensing cross-correlation, it will be necessary to resolve fainter AGN, and to use external constraints to break the degeneracy between baryonic feedback and cosmology. | future work 0.99 | 0.40 | 0.92 | asserted 0.71 |
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The paper
Original abstract
Baryonic feedback processes associated with galaxy formation directly influence the large-scale structure by redistributing gas. Recent measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect and eROSITA stacks of X-ray emission from optically-selected galaxy clusters suggest that feedback from Active Galactic Nuclei (AGN) is more efficient at expelling gas from low-mass clusters than previously thought. The measurement of the cross-correlation between cosmic shear and diffuse X-ray emission provides a new probe of the distribution of gas in groups and clusters. We use the FLAMINGO cosmological, hydrodynamical simulations to examine the X-ray--cosmic-shear cross-correlation. The cross-correlation is most sensitive to the distribution of gas in haloes with masses $10^{14}\leq M_{200\mathrm{c}}/\mathrm{M}_{\odot}\leq10^{15}$. It is sensitive to the strength of feedback, but the effects of variations in cosmology and baryonic physics are largely degenerate. We compare the FLAMINGO predictions with the cross-correlation between cosmic shear from the Dark Energy Survey and the ROSAT all-sky X-ray map. We account for AGN that would remain unresolved by ROSAT using either the direct FLAMINGO predictions or by abundance matching to the observed (extrapolated) AGN luminosity function. We find that the fiducial FLAMINGO model is in excellent agreement with the ROSAT--DES-Y3 cross-correlation, while models assuming weaker feedback and models with the significantly stronger feedback suggested by kSZ and eROSITA stacks are both incompatible with the observed X-ray--cosmic-shear cross-correlation.
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References
How the literature uses it
4 arXiv papers cite this in 9 sentences
What it cites · 45 sentences without a confident label
Uses the method or tool of 5 papers
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The $κ(θ)$ and $𝐗(θ)$ all-sky maps (including the binary mask for resolved point sources, if applicable) are then downgraded to $N_side=1024$ in order to match the angular resolution of the maps used by [ref] .
X-Ray-Cosmic-Shear Cross-Correlations: First Detection and Constraints on Baryonic Effects · Computing X-ray – lensing cross-correlations from FLAMINGO · 0.95
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We create an AGN contaminated X-ray all-sky map by combining both the AGN ($𝐗_AGN(θ)$) and hot gas ($𝐗_gas(θ)$) maps with the binary point source masking scheme employed by [ref] [Whilst not out-right specified in [ref] , we have confirmed via private communication that the same masking procedure and data is replicated in [ref] .].
2412.12081 · AGN contaminated X-ray all-sky maps · 0.99
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The individual photon flux maps are generated –the same way as all smoothed HEALPix maps [ref] – from the X-ray luminosities of `hot' gas particles, as detailed by [ref] , using emissivity tables from cloudy [ref] and are consistent with the radiative cooling rates of [ref] that are used in the FLAMINGO simulations.
Radiative cooling rates, ion fractions, molecule abundances and line emissivities including self-shielding and both local and metagalactic radiation fields · X-ray models and X-ray lightcone data · 0.98
Uses data or values from 2 papers
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We compute the $χ^2$ values using the covariance matrices of [ref] [The covariance matrices corresponding to the measurements of [ref] have been made publicly available by [ref] ] with 24 degrees of freedom per tomographic bin and 96 for the whole dataset.
X-Ray-Cosmic-Shear Cross-Correlations: First Detection and Constraints on Baryonic Effects · Comparison of the fiducial model to observations · 0.93
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We compute the $χ^2$ values using the covariance matrices of [ref] [The covariance matrices corresponding to the measurements of [ref] have been made publicly available by [ref] ] with 24 degrees of freedom per tomographic bin and 96 for the whole dataset.
2412.12081 · Comparison of the fiducial model to observations · 0.93
Compares with 2 papers
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In Fig. [ref] we show the predicted ROSAT–DES-Y3 cross-correlation for the L1$_$m9 simulation when the soft X-ray background is uncontaminated (solid curve) and when it is contaminated by unresolved AGN given by either the base FLAMINGO BHs (dotted curve) or abundance matched BHs (dashed curve and shaded regions) in comparison to the measurements of [ref] (triangle markers and error bars).
X-Ray-Cosmic-Shear Cross-Correlations: First Detection and Constraints on Baryonic Effects · Comparison of the fiducial model to observations · 0.96
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The joint modelling of kSZ measurements by [ref] (from the Atacama Cosmology Telescope [ref] , Planck and the Baryon Oscillation Spectroscopic Survey [ref] ) with cosmic shear data from KiDS-1000 [ref] and DES [ref] by [ref] and [ref] find a preference for stronger baryonic feedback (and lower cluster gas fractions) than prescribed by hydrodynamical simulations with cluster gas fractions akin to those of FLAMINGO's fiducial L1$_$m9 simulation.
2110.0222 · Comparing the X-ray–lensing cross-correlation to adjacent low redshift probes · 0.85
Cites as background 7 papers
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The range of angular scales, halo masses and redshifts that the angular (and 3D) power spectra from cosmic shear probes are sensitive to is well known [ref] , however, we have less intuition when it comes to diffuse X-ray emission.
2506.16434 · Decomposition of the soft X-ray flux · 0.95
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Additionally, X-ray auto- and cross-spectra have been forecast with semi-analytic models, halo occupation distribution (HOD) and halo model formalisms [ref] .
Forecasting Angular Cross Correlations Between Diffuse X-ray Emission and the Thermal Sunyaev-Zel'dovich Effect · Introduction · 0.84
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It is well understood that AGN dominate the soft X-ray background (CXB) and that unresolved AGN are the dominant contaminant in X-ray all-sky surveys [ref] .
Deep Extragalactic X-ray Surveys · AGN contaminated X-ray all-sky maps · 0.86
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