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Theoretical and observational studies have suggested that ram-pressure stripping (RPS) by the intracluster medium can be enhanced during cluster interactions, boosting the formation of the 'jellyfish' galaxies. In this work, we study the incidence of galaxies undergoing RPS in 52 clusters of different dynamical states. We use optical data from the WINGS/OmegaWINGS surveys and archival X-ray data to characterize the dynamical state of our cluster sample, applying eight different proxies. We then compute the number of RPS candidates relative to the infalling population of blue late-type galaxies within a fixed circular aperture in each cluster. We find no clear correlation between the fractions of RPS candidates and the different cluster dynamical state proxies considered. These fractions also show no apparent correlation with cluster mass. To construct a dynamical state classification closer to a merging 'sequence', we perform a visual classification of the dynamical states of the clusters, combining information available in optical, X-ray, and radio wavelengths. We find a mild increase in the RPS fraction in interacting clusters with respect to all other classes (including post-mergers). This mild enhancement could hint at a short-lived enhanced RPS in ongoing cluster mergers. However, our results are not statistically significant due to the low galaxy numbers. We note this is the first homogeneous attempt to quantify the effect of cluster dynamical state on RPS using a large cluster sample, but even larger (especially wider) multiwavelength surveys are needed to confirm the results. [ABSTRACT FROM AUTHOR]

Off-axis collisions between galaxy clusters may induce the phenomenon of sloshing, causing dense gas to be dragged from the cool core of a cluster, resulting in a spiral of enhanced X-ray emission. Abell 2199 displays signatures of sloshing in its core and it is possible that the orbital plane of the collision is seen nearly edge-on. We aim to evaluate whether the features of Abell 2199 can be explained by a sloshing spiral seen under a large inclination angle. To address this, we perform tailored hydrodynamical N -body simulations of a non-frontal collision with a galaxy group of |$M_{200}=1.6\times 10^{13}\, {\rm M_{\odot }}$|⁠. We obtain a suitable scenario in which the group passed by the main cluster core 0.8 Gyr ago, with a pericentric separation of 292 kpc. A good agreement is obtained from the temperature maps as well as the residuals from a β-model fit to the simulated X-ray emission. We find that under an inclination of i  = 70° the simulation results remain consistent with the observations. [ABSTRACT FROM AUTHOR]

While there are many ways to identify substructures in galaxy clusters using different wavelengths, each technique has its own caveat. In this paper, we conduct a detailed substructure search and dynamical state characterization of Abell 2399, a galaxy cluster in the local Universe (z ∼ 0.0579), by performing a multiwavelength analysis and testing the results through hydrodynamical simulations. In particular, we apply a Gaussian mixture model to the spectroscopic data from SDSS, WINGS, and OmegaWINGS Surveys to identify substructures. We further use public XMM–Newton data to investigate the intracluster medium (ICM) thermal properties, creating temperature, metallicity, entropy, and pressure maps. Finally, we run hydrodynamical simulations to constrain the merger stage of this system. The ICM is very asymmetrical and has regions of temperature and pressure enhancement that evidence a recent merging process. The optical substructure analysis retrieves the two main X-ray concentrations. The temperature, entropy, and pressure are smaller in the secondary clump than in the main clump. On the other hand, its metallicity is considerably higher. This result can be explained by the scenario found by the hydrodynamical simulations where the secondary clump passed very near to the centre of the main cluster possibly causing the galaxies of that region to release more metals through the increase of ram-pressure stripping. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of two merging clusters, from XMM–Newton X-ray archival data: PLCKESZ G036.7+14.9 (z  = 0.15; hereafter G036) and PLCK G292.5+22.0 (z  = 0.30; hereafter G292). We notice that the intracluster medium (ICM) is heated as a result of the merger, and we find evidence for a merger shock in the region between both subcluster haloes. X-ray observations confirm that the shocks in these systems are among the hottest known in the literature. From the ICM analysis of temperature discontinuity, the Mach numbers were determined to be M G036 = 1.3 ± 0.1 and M G292 = 1.47 ± 0.08 for G036 and G292, respectively. In this paper, for each cluster, we propose a hydrodynamic model for the merger as a whole, compatible with their diffuse X-ray emission and temperature maps. The simulations suggest that both clusters are observed shortly before pericentric passage. Our simulation results indicate that the merger of the G036 system is seen at an inclination of 50° (the angle between the plane of the orbit and the plane of the sky), and merely 50 Myr prior to the pericentric passage. In the case of G292, the subclusters would be merging not far from the plane of the sky (i  = 18°) and are observed 150 Myr before the two cores collide. [ABSTRACT FROM AUTHOR]

We analysed XMM – Newton EPIC data for 53 galaxy clusters. Through 2D spectral maps, we provide the most detailed and extended view of the spatial distribution of temperature (kT), pressure (P), entropy (S), and metallicity (Z) of galaxy clusters to date with the aim of correlating the dynamical state of the system to six cool-core (CC) diagnoses from the literature. With the objective of building 2D maps and resolving structures in kT, P, S, and Z, we divide the data in small regions from which spectra can be extracted. Our analysis shows that when clusters are spherically symmetric the CCs are preserved, the systems are relaxed with little signs of perturbation, and most of the CC criteria agree. The disturbed clusters are elongated, show clear signs of interaction in the 2D maps, and most do not have a CC. However, 16 well-studied clusters classified as CC by at least four criteria show spectral maps that appear disturbed. All of these clusters but one show clear signs of recent mergers, with a complex structure and geometry but with a CC that remains preserved. Thus, although very useful for CC characterization, most diagnoses are too simplistic to reproduce the overall structure and dynamics of galaxy clusters, and therefore the selection of relaxed systems according to these criteria may affect mass estimates. The complex structure of galaxy clusters can be reliably assessed through the 2D maps presented here. [ABSTRACT FROM AUTHOR]

Aims. Based on XMM-Newton, Chandra, and optical DR10-SDSS data, we investigate the metal enrichment history of the group NGC 4325 (z = 0.026). To complete the analysis we used chemical evolution models and studied the optical spectrum of the central dominant galaxy through its stellar population analysis and emission line diagnostics to analyse its role in the metal enrichment of the intra-group medium. Methods. We used X-ray 2D spectrally resolved maps to resolve structure in temperature and metallicity. We also derived gas and total masses within r2500 and r500 assuming hydrostatic equilibrium and spherical symmetry. To perform stellar population analysis we applied the spectral fitting technique with STARLIGHT to the optical spectrum of the central galaxy. We simulated the chemical evolution of the central galaxy. Results. While the temperature, pseudo-pressure, and pseudo-entropy maps showed no inhomogeneities, the spatial distribution of the metallicity shows a filamentary structure in the core of this group, which is spatially correlated with the central galaxy, suggesting a connection between the two. The analysis of the optical spectrum of the central galaxy showed no contribution by any recent AGN activity. Using the star formation history as input to chemical evolution models, we predicted the iron and oxygen mass released by supernovae (SNe) winds in the central galaxy up to the present time. Conclusions. Comparing the predicted amount of mass released by the NGC 4325 galaxy to the ones derived through X-ray analysis we conclude that the winds from the central galaxy alone play a minor role in the IGM metal enrichment of this group inside r2500. The SNe winds are responsible for no more than 3% of it and of the iron mass and 21% of the oxygen mass enclosed within r2500. Our results suggest that oxygen has been produced in the early stages of the group formation, becoming well mixed and leading to an almost flat profile. Instead, the iron distribution is centrally peaked, indicating that this element is still being added to the IGM specifically in the core by the SNIa. A possible scenario to explain the elongated metal-rich structure in the core of the NGC 4325 is a past AGN activity, in which our results suggest an episode older than ~107-108 yrs and younger than 5 × 108. Through the overall distribution of the galaxies, we found no signs of recent merger in the group centre that could explain the metal-rich structure. [ABSTRACT FROM AUTHOR]

Aims. Based on XMM-Newton, Chandra, and SDSS data, we investigate the baryon distribution in groups and clusters and its use as a cosmological constraint. For this, we considered a sample of 123 systems with temperatures kT500 = 1.0-9.0 keV, total masses in the mass range M500 = (∼1013-4 × 1015) h-1 70 M☉, and redshifts 0.02 < z < 1.3. Methods. The gas masses and total masses are derived from X-ray data under the assumption of hydrostatic equilibrium and spherical symmetry. The stellar masses are based on SDSS-DR8 optical photometric data. For the 37 systems out of 123 that had both optical and X-ray data available, we investigated the gas, stellar, and total baryon mass fractions inside r2500 and r500 and the differential gas mass fraction within the spherical annulus between r2500 and r500, as a function of total mass. For the other objects, we investigated the gas mass fraction only. Results. We find that the gas mass fraction inside r2500 and r500 depends on the total mass. However, the differential gas mass fraction does not show any dependence on total mass for systems with M500 > 1014 M☉. The stellar mass fraction inside r2500 and r500 increases towards low-mass systems more steeply than the fgas decrease with total mass. Adding the gas and stellar mass fractions to obtain the total baryonic content, we find it to increase with cluster mass, reaching the WMAP-7 value for clusters with M500 ∼ 1014 M☉. This led us to investigate the contribution of the intracluster light to the total baryon budget for lower mass systems, but we find that it cannot account for the difference observed. Conclusions. The gas mass fraction dependence on total mass observed for groups and clusters could be due to the difficulty of low-mass systems to retain gas inside the inner region (r < r2500). Because of their shallower potential well, non-thermal processes are more effective in expelling the gas from their central regions outwards. Since the differential gas mass fraction is nearly constant, it provides better constraints for cosmology. Moreover, we find that the gas mass fraction does not depend on redshift at a 2σ level. Using our total fb estimates, our results imply Ωm < 0.55, and taking the highest significant estimates for fb, Ωm > 0.22. [ABSTRACT FROM AUTHOR]