We present the statistical properties and the investigation on the origin of the scatter within the spatially resolved emission measure profiles of the CHEX–MATE sample, formed by 118 galaxy clusters ...selected via the SZ effect. These objects cover a wide mass, M YSZ 500 = 2-15×10 14 M ⊙ , and redshift, z=0.02, 0.6, range. They have been observed by XMM- Newton with a dedicated program that ensures an unprecedented homogeneous and high quality data. We leveraged this exceptional data set by studying the statistical properties of the surface brightness and emission measure radial profiles. We found that there is a critical scale, R~ 0.4 R YSZ 500 , within which the most morphologically relaxed and disturbed object profiles diverge. Above that radius these differences tend to be within 20%. We complemented the CHEX–MATE clusters with a twin sample drawn from the The Three Hundred suite of cosmological simulations. Leveraging this sample, we were able for the first time to investigate separately the scatter due to projection effects and the one due to cluster-to-cluster differences. We found that projection effects have a smaller impact on the scatter compared to object-to-object differences across all scales. Building on this, we found that below 0.4 R YSZ 500 , the scatter is of the order of 110% reflecting the wide plethora of gas distribution in cluster cores. The scatter is at its minimum, 0.56, in the intermediate range, 0.4-0.8 R YSZ 500 , despite their morphological status suggesting that clusters are close to the self-similar scenario within this radial range.
We study the dynamical state and the integrated total mass profiles of 75 massive (M500 > 5 × 1014 M⊙) Sunyaev–Zeldovich(SZ)-selected clusters at 0.08 < z < 1.1. The sample is built from the Planck ...catalogue, with the addition of four SPT clusters at z > 0.9. Using XMM-Newton imaging observations, we characterise the dynamical state with the centroid shift ⟨w⟩, the concentration CSB, and their combination, M, which simultaneously probes the core and the large-scale gas morphology. Using spatially resolved spectroscopy and assuming hydrostatic equilibrium, we derive the total integrated mass profiles. The mass profile shape is quantified by the sparsity, that is the ratio of M500 to M2500, the masses at density contrasts of 500 and 2500, respectively. We study the correlations between the various parameters and their dependence on redshift. We confirm that SZ-selected samples, thought to most accurately reflect the underlying cluster population, are dominated by disturbed and non-cool core objects at all redshifts. There is no significant evolution or mass dependence of either the cool core fraction or the centroid shift parameter. The M parameter evolves slightly with z, having a correlation coefficient of ρ = −0.2 ± 0.1 and a null hypothesis p-value of 0.01. In the high-mass regime considered here, the sparsity evolves minimally with redshift, increasing by 10% between z < 0.2 and z > 0.55, an effect that is significant at less than 2σ. In contrast, the dependence of the sparsity on dynamical state is much stronger, increasing by a factor of ∼60% from the one third most relaxed to the one third most disturbed objects, an effect that is significant at more than 3σ. This is the first observational evidence that the shape of the integrated total mass profile in massive clusters is principally governed by the dynamical state and is only mildly dependent on redshift. We discuss the consequences for the comparison between observations and theoretical predictions.
Aims. Imaging and spectroscopy of X-ray extended sources require a proper characterisation of a spatially unresolved background signal. This background includes sky and instrumental components, each ...of which are characterised by its proper spatial and spectral behaviour. While the X-ray sky background has been extensively studied in previous work, here we analyse and model the instrumental background of the ACIS-I detector on board the Chandra X-ray observatory in very faint mode. Methods. Caused by interaction of highly energetic particles with the detector, the ACIS-I instrumental background is spectrally characterised by the superimposition of several fluorescence emission lines onto a continuum. To isolate its flux from any sky component, we fitted an analytical model of the continuum to observations performed in very faint mode with the detector in the stowed position shielded from the sky, and gathered over the eight-year period starting in 2001. The remaining emission lines were fitted to blank-sky observations of the same period. We found 11 emission lines. Analysing the spatial variation of the amplitude, energy and width of these lines has further allowed us to infer that three lines of these are presumably due to an energy correction artefact produced in the frame store. Results. We provide an analytical model that predicts the instrumental background with a precision of 2% in the continuum and 5% in the lines. We use this model to measure the flux of the unresolved cosmic X-ray background in the Chandra deep field south. We obtain a flux of 10.2+0.5-0.4 × 10-13 erg cm-2 deg-2 s-1 for the 1−2 keV band and (3.8 ± 0.2) × 10-12 erg cm-2 deg-2 s-1 for the 2−8 keV band.
We present a detailed study of the integrated total hydrostatic mass profiles of the five most massive M500SZ < 5 × 1014 M⊙ ( M 500 SZ > 5 × 10 14 M ⊙ ) $\left( {M_{500}^{{\rm{SZ}}} > 5 \times ...{{10}^{14}}\,{M_ \odot }} \right)$ galaxy clusters selected at z ∼ 1 via the Sunyaev–Zel’dovich effect. These objects represent an ideal laboratory to test structure formation models where the primary driver is gravity. Optimally exploiting spatially-resolved spectroscopic information from XMM-Newton and Chandra observations, we used both parametric (forward, backward) and non-parametric methods to recover the mass profiles, finding that the results are extremely robust when density and temperature measurements are both available. Our X-ray masses at R500 are higher than the weak lensing masses obtained from the Hubble Space Telescope (HST), with a mean ratio of 1.39−0.35+0.47 1.39 − 0.35 + 0.47 $1.39^{+0.47}_{-0.35}$ . This offset goes in the opposite direction to that expected in a scenario where the hydrostatic method yields a biased, underestimated, mass. We investigated halo shape parameters such as sparsity and concentration, and compared to local X-ray selected clusters, finding hints for evolution in the central regions (or for selection effects). The total baryonic content is in agreement with the cosmic value at R500. Comparison with numerical simulations shows that the mass distribution and concentration are in line with expectations. These results illustrate the power of X-ray observations to probe the statistical properties of the gas and total mass profiles in this high mass, high-redshift regime.
ABSTRACT
We present new low-frequency (ν = 88–216 MHz) observations of the complex merging galaxy cluster Abell 3266. These new observations are taken with the Murchison Widefield Array (MWA) in its ...Phase II ‘extended’, long-baseline configuration, offering the highest resolution low-frequency view of the cluster to date. We report on the detection of four steep spectrum (α ≲ −1 for Sν ∝ να) extended radio sources within the cluster. We confirm the detection of a ∼570 kpc radio relic to the south of the cluster, and a possible bridge of emission connecting the relic to the cluster core. We also detect two new ultra-steep-spectrum (α ≲ −1.7) fossil plasma sources to the north and west of the cluster centre without associated compact radio emission. A previously detected radio galaxy in the cluster is also found to have a spectrally steepening tail with steep-spectrum components highlighted by the MWA. The timeline of the merger and the overall mass of the system are consistent with clusters hosting giant radio haloes, yet we do not detect a radio halo in Abell 3266. After simulating a range of radio haloes at 216 MHz, we place upper limits on the radio luminosity corresponding to ∼7.2 × 1024 W Hz−1 at 150 MHz assuming the expected 500 kpc radius – up to a factor of 5 lower than expected from scaling relations.
The prototype of the NIKA2 camera, NIKA, is a dual-band instrument operating at the IRAM 30-m telescope, which can observe the sky simultaneously at 150 and 260 GHz. One of the main goals of NIKA ...(and NIKA2) is to measure the pressure distribution in galaxy clusters at high angular resolution using the thermal Sunyaev-Zel’dovich (tSZ) effect. Such observations have already proved to be an excellent probe of cluster pressure distributions even at intermediate and high redshifts. However, an important fraction of clusters host sub-millimeter and/or radio point sources, which can significantly affect the reconstructed signal. Here we report on <20 arcsec angular resolution observations at 150 and 260 GHz of the cluster MACS J1423.8+2404, which hosts both radio and sub-millimeter point sources. We examine the morphological distribution of the tSZ signal and compare it to other datasets. The NIKA data are combined with Herschel satellite data to study the spectral energy distribution (SED) of the sub-millimeter point source contaminants. We then perform a joint reconstruction of the intracluster medium (ICM) electronic pressure and density by combining NIKA, Planck, XMM-Newton, and Chandra data, focusing on the impact of the radio and sub-millimeter sources on the reconstructed pressureprofile. We find that large-scale pressure distribution is unaffected by the point sources because of the resolved nature of the NIKA observations. The reconstructed pressure in the inner region is slightly higher when the contribution of point sources are removed. We show that it is not possible to set strong constraints on the central pressure distribution without accurately removing these contaminants. The comparison with X-ray only data shows good agreement for the pressure, temperature, and entropy profiles, which all indicate that MACS J1423.8+2404 is a dynamically relaxed cool core system. The present observations illustrate the possibility of measuring these quantities with a relatively small integration time, even at high redshift and without X-ray spectroscopy. This work is part of a pilot study aiming at optimizing tSZ observations with the future NIKA2 camera.
A radio bubble shredded by gas sloshing? Botteon, A; Gastaldello, F; ZuHone, J A ...
Monthly notices of the Royal Astronomical Society,
01/2024, Letnik:
527, Številka:
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ABSTRACT
We report on the detection of diffuse radio emission with peculiar morphology in the central region of the galaxy cluster Abell 2657. The most striking feature identified in our 144 MHz ...LOFAR image is a bifurcated radio arc that extends for a projected size of 150−200 kpc. From the analysis of XMM-Newton data, we find clear evidence of gas sloshing in the cluster and a possible dip in X-ray surface brightness between the two radio arcs which deserves confirmation. Interestingly, the synchrotron emission of the bifurcated radio arc is stretched along the sloshing spiral. We compare our observational results with numerical simulations of non-thermal components interacting with gas motions. We suggest that the detected emission may trace a radio bubble shredded by gas sloshing, where relativistic electrons and magnetic fields are expected to be stretched and stirred as a consequence of tangential flows induced by the spiralling gas motion. Lastly, we report on the presence of two thin (6−7 kpc in width) and parallel strands of radio emission embedded in the outer arc that are morphologically similar to the emerging population of non-thermal filaments observed in galaxy clusters, radio galaxies, and the Galactic centre. While this work further demonstrates the complex interplay between thermal and non-thermal components in the intracluster medium, follow-up observations in radio and X-rays are required to firmly determine the origin of the features observed in Abell 2657.
Aims. The goal of this work is to devise a description of the enrichment process in large-scale structure that explains the available observations and makes predictions for future measurements. ...Methods. We took a spartan approach to this study, employing observational results and algebra to connect stellar assembly in star-forming halos with metal enrichment of the intra-cluster and group medium. Results. On one hand, our construct is the first to provide an explanation for much of the phenomenology of metal enrichment in clusters and groups. It sheds light on the lack of redshift evolution in metal abundance, as well as the small scatter of metal abundance profiles, the entropy versus abundance anti-correlation found in cool core clusters, and the so-called Fe conundrum, along with several other aspects of cluster enrichment. On the other hand, it also allows us to infer the properties of other constituents of large-scale structure. We find that gas that is not bound to halos must have a metal abundance similar to that of the ICM and only about one-seventh to one-third of the Fe in the Universe is locked in stars. A comparable amount is found in gas in groups and clusters and, lastly and most importantly, about three-fifths of the total Fe is contained in a tenuous warm or hot gaseous medium in or between galaxies. We point out that several of our results follow from two critical but well motivated assumptions: 1) the stellar mass in massive halos is currently underestimated and 2) the adopted Fe yield is only marginally consistent with predictions from synthesis models and SN rates. Conclusions. One of the most appealing features of the work presented here is that it provides an observationally grounded construct where vital questions on chemical enrichment in the large-scale structure can be addressed. We hope that it may serve as a useful baseline for future works.
We examined the reconstruction of galaxy cluster radial density profiles obtained from Chandra and XMM-Newton X-ray observations, using high quality data for a sample of twelve objects covering a ...range of morphologies and redshifts. By comparing the results obtained from the two observatories and by varying key aspects of the analysis procedure, we examined the impact of instrumental effects and of differences in the methodology used in the recovery of the density profiles. We find that the final density profile shape is particularly robust. We adapted the photon weighting vignetting correction method developed for XMM-Newton for use with Chandra data, and confirm that the resulting Chandra profiles are consistent with those corrected a posteriori for vignetting effects. Profiles obtained from direct deprojection and those derived using parametric models are consistent at the 1% level. At radii larger than ~6″, the agreement between Chandra and XMM-Newton is better than 1%, confirming an excellent understanding of the XMM-Newton PSF. Furthermore, we find no significant energy dependence. The impact of the well-known offset between Chandra and XMM-Newton gas temperature determinations on the density profiles is found to be negligible. However, we find an overall normalisation offset in density profiles of the order of ~2.5%, which is linked to absolute flux cross-calibration issues. As a final result, the weighted ratios of Chandra to XMM-Newton gas masses computed at R2500 and R500 are r = 1.03 ± 0.01 and r = 1.03 ± 0.03, respectively. Our study confirms that the radial density profiles are robustly recovered, and that any differences between Chandra and XMM-Newton can be constrained to the ~2.5% level, regardless of the exact data analysis details. These encouraging results open the way for the true combination of X-ray observations of galaxy clusters, fully leveraging the high resolution of Chandra and the high throughput of XMM-Newton.
An accurate reconstruction of galaxy cluster masses is key to use this population of objects as a cosmological probe. In this work we present a study on the hydrostatic-to-lensing mass scaling ...relation for a sample of 53 clusters whose masses were reconstructed homogeneously in a redshift range between z = 0.05 and 1.07. The M 500 mass for each cluster was indeed inferred from the mass profiles extracted from the X-ray and lensing data, without using a priori observable-mass scaling relations. We assessed the systematic dispersion of the masses estimated with our reference analyses with respect to other published mass estimates. Accounting for this systematic scatter does not change our main results, but enables the propagation of the uncertainties related to the mass reconstruction method or used dataset. Our analysis gives a hydrostatic-to-lensing mass bias of (1− b ) = 0.739 −0.070 +0.075 and no evidence of evolution with redshift. These results are robust against possible subsample differences.
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