Observations Of Galaxy Clusters Research Articles

Dianoga SIDM: Galaxy cluster self-interacting dark matter simulations

Self-interacting dark matter (SIDM) can tackle or alleviate small-scale issues within the cosmological standard model Lambda CDM, and diverse flavours of SIDM can produce unique astrophysical predictions, resulting in different possible signatures which can be used to test these models with dedicated observations of galaxy clusters This work aims to assess the impact of dark matter self-interactions on the properties of galaxy clusters. In particular, the goal is to study the angular dependence of the cross section by testing rare (large angle scattering) and frequent (small angle scattering) SIDM models with velocity-dependent cross sections. We re-simulated six galaxy cluster zoom-in initial conditions with a dark matter-only run and with full-physics set-up simulations that include a self-consistent treatment of baryon physics. We tested the dark matter-only setup and the full physics setup with the collisionless cold dark matter, rare self-interacting dark matter, and frequent self-interacting dark matter models. We then studied their matter density profiles as well as their subhalo population. Our dark matter-only SIDM simulations agree with theoretical models, and when baryons are included in simulations, our SIDM models substantially increase the central density of galaxy cluster cores compared to full-physics simulations using collisionless dark matter. SIDM subhalo suppression in full-physics simulations is milder compared to the one found in the dark matter-only simulations because of the cuspier baryonic potential that prevents subhalo disruption. Moreover, SIDM with small-angle scattering significantly suppresses a larger number of subhaloes compared to large-angle scattering SIDM models. Additionally, SIDM models generate a broader range of subhalo concentration values, including a tail of more diffuse subhaloes in the outskirts of galaxy clusters and a population of more compact subhaloes in the cluster cores.

Fast emulation of two-point angular statistics for photometric galaxy surveys

Abstract We develop a set of machine-learning based cosmological emulators, to obtain fast model predictions for the C(ℓ) angular power spectrum coefficients, characterising tomographic observations of galaxy clustering and weak gravitational lensing from multi-band photometric surveys (and their cross-correlation). A set of neural networks are trained to map cosmological parameters into the coefficients, achieving, with respect to standard Boltzmann solvers, a speed-up of $\mathcal {O}(10^3)$ in computing the required statistics for a given set of cosmological parameters, with an accuracy better than 0.175% (<0.1% for the weak lensing case). This corresponds to $\lesssim 2~{{\%}}$ of the statistical error bars expected from a typical Stage IV photometric surveys. Such overall improvement in speed and accuracy is obtained through (i) a specific pre-processing optimisation, ahead of the training phase, and (ii) an effective neural network architecture. Compared to previous implementations in the literature, we achieve an improvement of a factor of 5 in terms of accuracy, while training a considerably lower amount of neural networks. This results in a cheaper training procedure and a higher computational performance. Finally, we show that our emulators can recover unbiased posteriors when analysing synthetic Stage-IV galaxy survey datasets.

The case for hot-mode accretion in Abell 2029

Abstract Radiative cooling and AGN heating are thought to form a feedback loop that regulates the evolution of low redshift cool-core galaxy clusters. Numerical simulations suggest that formation of multiphase gas in the cluster core imposes a floor on the ratio of cooling time (tcool) to free-fall time (tff) at min (tcool/tff) ≈ 10. Observations of galaxy clusters show evidence for such a floor, and usually the cluster cores with min (tcool/tff) ≲ 30 contain abundant multiphase gas. However, there are important outliers. One of them is Abell 2029, a massive galaxy cluster (M200 ≳ 1015 M⊙) with min (tcool/tff) ∼ 20, but little apparent multiphase gas. In this paper, we present high resolution 3D hydrodynamic AMR simulations of a cluster similar to A2029 and study how it evolves over a period of 1-2 Gyr. Those simulations suggest that Abell 2029 self-regulates without producing multiphase gas because the mass of its central black hole (∼5 × 1010 M⊙) is great enough for Bondi accretion of hot ambient gas to produce enough feedback energy to compensate for radiative cooling.

A Hubble constant estimate from galaxy cluster and type Ia SNe observations

In this work, we constrain the Hubble constant parameter, H 0, using a combination of the Pantheon sample and galaxy clusters (GC) measurements from minimal cosmological assumptions. Assuming the validity of the cosmic distance duality relation, an estimator is created for H 0 that only depends on simple geometrical distances, which is evaluated from Pantheon and a GC angular diameter distance sample afterward. The statistical and systematic errors in GC measurements are summed in quadrature in our analysis. We find H 0 = 67.22 ± 6.07 km s-1 Mpc-1 in 1σ confidence level (C.L.). This measurement presents an error of around 9%, showing that future and better GC measurements can shed light on the current Hubble tension.

Simulating the LOcal Web (SLOW) II. Properties of local galaxy clusters

This is the second paper in a series presenting the results from a 500 $h^ $Mpc large constrained simulation of the local Universe (SLOW). The initial conditions for this cosmological hydro-dynamical simulation are based on peculiar velocities derived from the CosmicFlows-2 catalog. The simulation follows cooling, star formation, and the evolution of super-massive black holes. This allows one to directly predict observable properties of the intracluster medium (ICM) within galaxy clusters, including X-ray luminosity, temperatures, and the Compton-y signal. Comparing the properties of observed galaxy clusters within the local Universe with the properties of their simulated counterparts enables us to assess the effectiveness of the initial condition constraints in accurately replicating the mildly nonlinear properties of the largest, collapsed objects within the simulation. Based on the combination of several, publicly available surveys we compiled a sample of galaxy clusters within the local Universe, of which we were able to cross-identify 46 of them with an associated counterpart within the SLOW simulation. We then derived the probability of the cross identification based on mass, X-ray luminosity, temperature, and Compton-y by comparing it to a random selection. Our set of 46 cross-identified local Universe clusters contains the 13 most massive clusters from the Planck SZ catalog as well as 70<!PCT!> of clusters with $M_ $ larger than $2 $ M$_ odot $. Compared to previous constrained simulations of the local volume, we found in SLOW a much larger amount of replicated galaxy clusters, where their simulation-based mass prediction falls within the uncertainties of the observational mass estimates. Comparing the median observed and simulated masses of our cross-identified sample allows us to independently deduce a hydrostatic mass bias of $(1-b) approx0.87$. The SLOW constrained simulation of the local Universe faithfully reproduces numerous fundamental characteristics of a sizable number of galaxy clusters within our local neighborhood, opening a new avenue for studying the formation and evolution of a large set of individual galaxy clusters as well as testing our understanding of physical processes governing the ICM.

Study of dependence of ram pressure stripping on the orbital parameters of the galaxies

ABSTRACT Comprehensive observations of galaxy clusters suggest that gas deficiency in the galaxies could be due to ram pressure stripping due to the high-pressure intra-cluster medium acting on the galactic discs. The presence of gas in galaxies is essential for star formation. The net force due to ram pressure is dependent on the ambient medium and the orbit followed by the galaxy as it moves past the cluster medium. This work deals with the effect of non-radial orbits of galaxies and the inclination of the disc plane of galaxies with the orbital plane on the mass of gas removed due to ram pressure. This gives a realistic approach to understanding the process of ram pressure stripping. The orbital parameters are extracted from eagle simulation data set along with the mass distribution of the galaxies. The analytical model proposed by Singh et. al. is modified appropriately to include the effect of the inclination angle. The non-radial orbits and infalling galaxies not being face-on decrease the amount of gas removed. Moreover, the inclination angle has a pronounced effect on the stripping of gas in low-mass galaxies as compared to high-mass galaxies with similar inclinations. The results show that the efficiency of the ram pressure stripping can be much lower in some cases, and hence gas in infalling galaxies can survive for much longer than expected from a simple analysis.

Modeling neutrino-induced scale-dependent galaxy clustering for photometric galaxy surveys

The increasing statistical precision of photometric redshift surveys requires improved accuracy of theoretical predictions for large-scale structure observables to obtain unbiased cosmological constraints. In ΛCDM cosmologies, massive neutrinos stream freely at small cosmological scales, suppressing the small-scale power spectrum. In massive neutrino cosmologies, galaxy bias modeling needs to accurately relate the scale-dependent growth of the underlying matter field to observed galaxy clustering statistics. In this work, we implement a computationally efficient approximation of the neutrino-induced scale-dependent bias (NISDB). Through simulated likelihood analyses of Dark Energy Survey Year 3 (DESY3) and Legacy Survey of Space and Time Year 1 (LSSTY1) synthetic data that contain an appreciable NISDB, we examine the impact of linear galaxy bias and neutrino mass modeling choices on cosmological parameter inference. We find model misspecification of the NISDB approximation and neutrino mass models to decrease the constraining power of photometric galaxy surveys and cause parameter biases in the cosmological interpretation of future surveys. We quantify these biases and devise mitigation strategies.

First evidence of a connection between cluster-scale diffuse radio emission in cool-core galaxy clusters and sloshing features

Radio observations of a few cool-core galaxy clusters have revealed the presence of diffuse emission on cluster scales, similar to what was found in merging clusters in the form of radio halos. These sources might suggest that a minor merger, while not sufficiently energetic to disrupt the cool core, could still trigger particle acceleration in the intracluster medium on scales of hundreds of kiloparsecs. We aim to verify the occurrence of cluster-scale diffuse radio emission in cool-core clusters and test the minor merger scenario. With the LOw Frequency ARray (LOFAR) at 144 MHz, we observed a sample of twelve cool-core galaxy clusters presenting some level of dynamical disturbances, according to X-ray data. We also performed a systematic search of cold fronts in these clusters, re-analysing archival Chandra observations. The clusters PSZ1G139.61+24, A1068 (new detection), MS 1455.0+2232, and RX J1720.1+2638 present diffuse radio emission on a cluster scale ($r $). This emission is characterised by a double component: a central mini-halo confined by cold fronts and diffuse emission on larger scales, whose radio power at 144 MHz is comparable to that of radio halos detected in merging systems with the same cluster mass. The cold fronts in A1068 are a new detection. We also found a candidate plasma depletion layer in this cluster. No sloshing features are found in the other eight clusters. Two of them present a mini-halo, with diffuse radio emission confined to the cluster core. We also found a new candidate mini-halo. Whereas, for the remaining five clusters, we did not detect halo-like emission. For clusters without cluster-scale halos, we derived upper limits to the radio halo power. We found that cluster-scale diffuse radio emission is not present in all cool-core clusters when observed at a low frequency, but it is correlated to the presence of cold fronts. The coexistence of cluster-scale diffuse radio emission and cold fronts in cool-core clusters requires a specific configuration of the merger and so it puts some constraints on the turbulence, which deserves to be investigated in the future with theoretical works.

Characterising the intra-cluster light in The Three Hundred simulations

We characterise the intra-cluster light (ICL) in ensembles of full-physics cluster simulations from THE THREE HUNDRED project, a suite of 324 hydrodynamical resimulations of cluster-sized halos. We identify the ICL as those stellar particles bound to the potential of the cluster itself, but not to any of its substructures, and separate the brightest cluster galaxy (BCG) by means of a fixed 50 kpc aperture. We find the total BCG+ICL mass to be in agreement with state-of-the-art observations of galaxy clusters. The ICL mass fraction of our clusters is between 30 and 50% of the total stellar mass within R500, while the BCG represents around 10%. We further find no trend of the ICL fraction with cluster halo mass, at least not in the range [0.2, 3] 1015 h−1 M⊙ considered here. For the dynamical state, characterised both by theoretical estimators and by the recent merging history of the cluster, there is a clear correlation, such that more relaxed clusters and those that have undergone fewer recent mergers have a higher ICL fraction. Finally, we investigate the possibility of using the ICL to explore the dark matter (DM) component of galaxy clusters. We compute the volumetric density profile for the DM and ICL components and show that, up to R500, the ratio between the two can be described by a power law. Working with the velocity dispersion profiles instead, we show that the ratio can be fit by a straight line. Providing the parameters of these fits, we show how the ICL can be used to infer DM properties.

Constraining decaying very heavy dark matter from galaxy clusters with 14 year Fermi-LAT data

Galaxy clusters are promising targets for indirect detection of dark matter thanks to the large dark matter content. Using 14 years of Fermi-LAT data from seven nearby galaxy clusters, we obtain constraints on the lifetime of decaying very heavy dark matter particles with masses ranging from 103 GeV to 1016 GeV. We consider a variety of decaying channels and calculate prompt gamma rays and electrons/positrons from the dark matter. Furthermore, we take into account electromagnetic cascades induced by the primary gamma rays and electrons/positrons, and search for the resulting gamma-ray signals from the directions of the galaxy clusters. We adopt a Navarro-Frenk-White profile of the dark matter halos, and use the profile likelihood method to set lower limits on the dark matter lifetime at a 95% confidence level. Our results are competitive with those obtained through other gamma-ray observations of galaxy clusters and provide complementary constraints to existing indirect searches for decaying very heavy dark matter.

Flat-sky angular power spectra revisited

We revisit the flat-sky approximation for evaluating the angular power spectra of projected random fields by retaining information about the correlations along the line of sight. For the case of projections with broad, overlapping radial window functions, these line-of-sight correlations are suppressed and are ignored in the commonly adopted Limber approximation. However, retaining the correlations is important for narrow window functions or unequal-time spectra but introduces significant computational difficulties due to the highly oscillatory nature of the integrands involved. We deal with the integral over line-of-sight wave-modes in the flat-sky approximation analytically, using the FFTlog expansion of the 3D power spectrum. This results in an efficient computational method, which is a substantial improvement compared to any full-sky approaches. We apply our results to galaxy clustering (with and without redshift-space distortions), CMB lensing and galaxy lensing observables in a flat ΛCDM universe. In the case of galaxy clustering, we find excellent agreement with the full-sky results on large (percent-level agreement) and intermediate or small (subpercent agreement) scales, dramatically out-performing the Limber approximation for both wide and narrow window functions, and in equal- and unequal-time cases. In the cases of lensing, we show on the full-sky that the angular power spectrum of the lensing convergence can be very well approximated by projecting the 3D Laplacian (rather than the correct angular Laplacian) of the gravitational potential, even on large scales. Combining this approximation with our flat-sky techniques provides an efficient and accurate evaluation of the CMB lensing angular power spectrum on all scales. We further analyse the clustering and lensing angular power spectra by isolating the projection effects due to the observable- and survey-specific window functions, separating them from the effects due to integration along the line of sight and unequal-time mixing in the 3D power spectrum. All of the angular power spectrum results presented in this paper are obtained using a Python code implementation, which we make publicly available.

The three hundred project: mapping the matter distribution in galaxy clusters via deep learning from multiview simulated observations

ABSTRACT A galaxy cluster as the most massive gravitationally bound object in the Universe, is dominated by dark matter, which unfortunately can only be investigated through its interaction with the luminous baryons with some simplified assumptions that introduce an un-preferred bias. In this work, we, for the first time, propose a deep learning method based on the U-Net architecture, to directly infer the projected total mass density map from idealized observations of simulated galaxy clusters at multiwavelengths. The model is trained with a large data set of simulated images from clusters of the three hundred project. Although machine learning (ML) models do not depend on the assumptions of the dynamics of the intracluster medium, our whole method relies on the choice of the physics implemented in the hydrodynamic simulations, which is a limitation of the method. Through different metrics to assess the fidelity of the inferred density map, we show that the predicted total mass distribution is in very good agreement with the true simulated cluster. Therefore, it is not surprising to see the integrated halo mass is almost unbiased, around 1 per cent for the best result from multiview, and the scatter is also very small, basically within 3 per cent. This result suggests that this ML method provides an alternative and more accessible approach to reconstructing the overall matter distribution in galaxy clusters, which can complement the lensing method.

Imprints of dark matter–massive neutrino interaction in upcoming post-reionization and galaxy surveys

ABSTRACT We explore possible signatures of the interaction between dark matter (DM) and massive neutrinos during the post-reionization epoch. Using both Fisher matrix forecast analysis and Markov chain Monte Carlo simulation, we conduct a thorough investigation of the constraints and imprints of the scenario on the upcoming post-reionization and galaxy surveys. Our investigation focuses on two key parameters: the strength of the DM–massive neutrino interaction (u) and the total neutrino mass (Mtot), on top of the usual six cosmological parameters. We utilize future 21-cm intensity mapping, galaxy clustering, and cosmic shear observations in order to investigate the possible constraints of these parameters in the future observations: Square Kilometre Array (SKA1 and SKA2) and Euclid, taking both conservative and realistic approaches. All these missions show promise in constraining both the parameters u and Mtot by few orders compared to the current constraints from Planck18 (SKA2 performing the best among them). Although we do not find much improvement in H0 and σ8 tensions from our forecast analysis, SKA2 constrains them better in conservative approach. We further perform a brief investigation of the prospects of some of the next-generation cosmic microwave background (CMB) missions in combinations with large-scale structure experiments in improving the constraints. Our analysis reveals that both SKA2 and CMB-S4 (Cosmic Microwave Background Stage-4) + Euclid + SKA1 IM2 (Square Kilometre Array1 Intensity Mapping Band2) combination will put the strongest bounds on the model parameters.

A persistent excess of galaxy-galaxy strong lensing observed in galaxy clusters

Context. Previous studies have revealed that the estimated probability of galaxy-galaxy strong lensing in observed galaxy clusters exceeds the expectations from the Λ cold dark matter cosmological model by one order of magnitude. Aims. We aim to understand the origin of this excess by analyzing a larger set of simulated galaxy clusters, and investigating how the theoretical expectations vary under different adopted prescriptions and numerical implementations of star formation and feedback in simulations. Methods. We performed a ray-tracing analysis of 324 galaxy clusters from the THREE HUNDRED project, comparing the GADGET-X and GIZMO-SIMBA runs. These simulations, which start from the same initial conditions, were performed with different implementations of hydrodynamics and galaxy formation models tailored to match different observational properties of the intracluster medium and cluster galaxies. Results. We find that galaxies in the GIZMO-SIMBA simulations develop denser stellar cores than their GADGET-X counterparts. Consequently, their probability for galaxy-galaxy strong lensing is higher by a factor of ∼3. This increment is still insufficient to fill the gap with observations as a discrepancy by a factor ∼4 still persists. In addition, we find that several simulated galaxies have Einstein radii that are too large compared to observations. Conclusions. We conclude that a persistent excess of galaxy-galaxy strong lensing exists in observed galaxy clusters. The origin of this discrepancy with theoretical predictions is still unexplained in the framework of the cosmological hydrodynamical simulations. This might signal a hitherto unknown issue with either the simulation methods or our assumptions regarding the standard cosmological model.

4K × 4K CCD Imager for the 3.6 m DOT: Recent Up-gradations and Results

The 4K × 4K CCD Imager is the first light instrument for the 3.6[Formula: see text]m Devasthal Optical Telescope and is producing broad-band imaging observations of many Galactic and extra-galactic sources since 2015–2016. Capabilities of the CCD Imager are demonstrated recently through several publications using the well-calibrated multi-band deep photometric results as expected from other similar facilities globally. In this paper, we summarize some of the recent up-gradations made to improve the Imager, i.e. mounting the new filter wheel casing, replacing stray light baffles and discussing the fringe pattern corrections in redder filters. Some of the new science initiatives like galaxy-embedded faint point sources including WR stars and the observations of low surface brightness galaxy clusters are also discussed.

Lensing in the Blue. II. Estimating the Sensitivity of Stratospheric Balloons to Weak Gravitational Lensing

The Superpressure Balloon-borne Imaging Telescope (SuperBIT) is a diffraction-limited, wide-field, 0.5 m, near-infrared to near-ultraviolet observatory designed to exploit the stratosphere’s space-like conditions. SuperBIT’s 2023 science flight will deliver deep, blue imaging of galaxy clusters for gravitational lensing analysis. In preparation, we have developed a weak-lensing measurement pipeline with modern algorithms for PSF characterization, shape measurement, and shear calibration. We validate our pipeline and forecast SuperBIT survey properties with simulated galaxy cluster observations in SuperBIT’s near-UV and blue bandpasses. We predict imaging depth, galaxy number (source) density, and redshift distribution for observations in SuperBIT’s three bluest filters; the effect of lensing sample selections is also considered. We find that, in three hours of on-sky integration, SuperBIT can attain a depth of b = 26 mag and a total source density exceeding 40 galaxies per square arcminute. Even with the application of lensing-analysis catalog selections, we find b-band source densities between 25 and 30 galaxies per square arcminute with a median redshift of z = 1.1. Our analysis confirms SuperBIT’s capability for weak gravitational lensing measurements in the blue.

Self-interacting dark matter on small and large scales

In the self-interacting dark matter paradigm (hereafter SIDM), dark matter (DM) is assumed to have non-gravitational interactions with itself. SIDM has been constrained by observations of galaxy clusters. More recently, measurements of large DM densities at the center of the Milky Way’s galaxy satellites are indicating that DM-DM interactions can potentially induce gravothermal core collapse. In this proceeding an overview of the combined measurements of cluster-size galaxies and kinematics of local satellite galaxies is used to argue that DM interactions should depend on the relative velocity of the DM particles.

KiDS-1000: Combined halo-model cosmology constraints from galaxy abundance, galaxy clustering, and galaxy-galaxy lensing

We present constraints on the flat Λ cold dark matter cosmological model through a joint analysis of galaxy abundance, galaxy clustering, and galaxy-galaxy lensing observables with the Kilo-Degree Survey. Our theoretical model combines a flexible conditional stellar mass function, which describes the galaxy-halo connection, with a cosmological N-body simulation-calibrated halo model, which describes the non-linear matter field. Our magnitude-limited bright galaxy sample combines nine-band optical-to-near-infrared photometry with an extensive and complete spectroscopic training sample to provide accurate redshift and stellar mass estimates. Our faint galaxy sample provides a background of accurately calibrated lensing measurements. We constrain the structure growth parameter to S8 = σ8√Ωm/0.3 =√0.773−0.030+0.028 and the matter density parameter to Ωm = 0.290−0.017+0.021. The galaxy-halo connection model adopted in the work is shown to be in agreement with previous studies. Our constraints on cosmological parameters are comparable to, and consistent with, joint ‘3 × 2pt’ clustering-lensing analyses that additionally include a cosmic shear observable. This analysis therefore brings attention to the significant constraining power in the often excluded non-linear scales for galaxy clustering and galaxy-galaxy lensing observables. By adopting a theoretical model that accounts for non-linear halo bias, halo exclusion, scale-dependent galaxy bias, and the impact of baryon feedback, this work demonstrates the potential for, and a way towards, including non-linear scales in cosmological analyses. Varying the width of the satellite galaxy distribution with an additional parameter yields a strong preference for sub-Poissonian variance, improving the goodness of fit by 0.18 in terms of the reduced χ2 value (and increasing the p-value by 0.25) compared to a fixed Poisson distribution.

Radio continuum tails in ram pressure-stripped spiral galaxies: Experimenting with a semi-empirical model in Abell 2255

Context. Wide-field radio continuum observations of galaxy clusters are revealing an increasing number of spiral galaxies hosting tens of kiloparsec-length radio tails produced by the displacement of nonthermal interstellar medium (ISM) by ram pressure. Aims. We present a semi-empirical model for the multifrequency radio continuum emission from ram-pressure-stripped tails based on the pure synchrotron cooling of a radio plasma moving along the stripping direction with a uniform velocity. Methods. We combine LOFAR and uGMRT observations at 144 and 400 MHz to study the flux density and spectral index profiles of the radio tails of seven galaxies in Abell 2255, and use the model to reproduce the flux density and spectral index profiles, and infer the stripped radio plasma velocity. Results. For five out of these seven galaxies, we observe a monotonic decrease in both flux density and spectral index up to 30 kpc from their stellar disk. Our model reproduces the observed trends with a projected radio plasma bulk velocity of between 160 and 430 km s−1. This result represents the first indirect measurement of the stripped, nonthermal ISM velocity. The observed spectral index trends indicate that the synchrotron cooling is faster than the adiabatic expansion losses, suggesting that the stripped radio plasma can survive for a few tens of million years outside of the stellar disk. This provides a lower limit on the lifetime of the stripped ISM outside of the disk. As a proof of concept, we use the best-fit velocities to constrain the 3D velocity of the galaxies in the cluster to be in the range of 300−1300 km s−1. We estimate the ram pressure affecting these galaxies to be between 0.1 and 2.9 × 10−11 erg cm−3, and measure the inclination between their stellar disk and the ram pressure wind.

The XXL Survey

Context. X-ray observations of galaxy clusters are impacted by the presence of active galactic nuclei (AGNs) in a manner that is challenging to quantify, leading to biases in the detection and measurement of cluster properties for both astrophysics and cosmological applications. Aims. We detect and characterise clusters contaminated by central AGNs within the XXL survey footprint and provide a systematic assessment of the cosmological impact of such systems in X-ray cluster samples. Methods. We introduce a new automated class for AGN-contaminated (AC) clusters in the XXL source detection pipeline. The majority of these systems are otherwise missed by current X-ray cluster-detection methods. The AC selection is also effective in distinguishing AGN and cool-core presence using supplementary optical and infrared information. Results. We present 33 AC objects, including 25 clusters in the redshift range, 0.14 ≤ z ≤ 1.03, and eight other sources with significantly peaked central profiles based on X-ray observations. Six of these are new confirmed clusters. We computed the missed fraction of the XXL survey, which is defined as the fraction of genuine clusters that are undetected due to their centrally peaked X-ray profiles. We report seven undetected AC clusters above z > 0.6, in the range where X-ray cluster detection efficiency drops significantly. The missed fraction is estimated to be at the level of 5% for the 50 square-degree XXL area. The impact on cosmological estimates from missed clusters is negligible for XXL, but it produces a tension of ∼3σ with the fiducial cosmology when considering larger survey areas. Conclusions. This work demonstrates the first systematic attempt to quantify the percentage of missed clusters in X-ray surveys as a result of central AGN contamination. Looking towards surveys such as eROSITA and Athena, larger areas and increased sensitivity will significantly enhance cluster detection, and therefore robust methods for characterising AGN contamination will be crucial for precise cluster cosmology, particularly in the redshift z > 1 regime.