Active and passive shielding design optimization and technical solutions for deep sensitivity hard X-ray focusing telescopes

The 10-100 keV region of the electromagnetic spectrum contains the potential for a dramatic improvement in our understanding of a number of key problems in high energy astrophysics. A deep inspection of the universe in this band is on the other hand still lacking because of the demanding sensitivity (fraction of microCrab in the 20-40 keV for 1 Ms integration time) and imaging (~15" angular resolution) requirements. The mission ideas currently being proposed are based on long focal length, grazing incidence, multi-layer optics, coupled with focal plane detectors with few hundreds microns spatial resolution capability. The required large focal lengths, ranging between 8 and 50 m, can be realized by means of extendable optical benches (as foreseen e.g. for the HEXIT-SAT, NEXT and NuSTAR missions) or formation flight scenarios (e.g. Simbol-X and XEUS). While the final telescope design will require a detailed trade-off analysis between all the relevant parameters (focal length, plate scale value, angular resolution, field of view, detector size, and sensitivity degradation due to detector dead area and telescope vignetting), extreme attention must be dedicated to the background minimization. In this respect, key issues are represented by the passive baffling system, which in case of large focal lengths requires particular design assessments, and by the active/passive shielding geometries and materials. In this work, the result of a study of the expected background for a hard X-ray telescope is presented, and its implication on the required sensitivity, together with the possible implementation design concepts for active and passive shielding in the framework of future satellite missions, are discussed.Comment: 13 pages, 6 figures. Proceedings of SPIE conference "Optics for EUV, X-Ray, and Gamma-Ray Astronomy II", San Diego (CA, USA), July 31st - August 4th, 2005, Vol. 5900. Full color figures are available at http://www.bo.iasf.cnr.it/~malaguti/papers/SPIE2005_1.ps.g

AMICO galaxy clusters in KiDS-DR3: Constraints on ΛCDM from extreme value statistics

We constrain the ΛCDM cosmological parameter s(8) by applying the extreme value statistics for galaxy cluster mass on the AMICO KiDS-DR3 catalogue. We sample the posterior distribution of the parameters by considering the likelihood of observing the largest cluster mass value in a sample of N-obs = 3644 clusters with intrinsic richness λ(*) > 20 in the redshift range z ∈ [0.10, 0.60]. We obtain s(8) = 0 . 90( + 0 .20) (-0.18), consistent within 1s with the measurements obtained by the Planck collaboration and with previous results from cluster cosmology exploiting AMICO KiDS-DR3. The constraints could improve by applying this method to forthcoming missions, such as Euclid and LSST, which are expected to deliver thousands of distant and massive clusters

AMICO galaxy clusters in KiDS-DR3: Cosmological constraints from angular power spectrum and correlation function

We study the tomographic clustering properties of the photometric cluster catalogue derived from the Third Data Release of the Kilo Degree Survey, focusing on the angular correlation function and its spherical harmonic counterpart, the angular power spectrum. We measure the angular correlation function and power spectrum from a sample of 5162 clusters, with an intrinsic richness $\lambda^*\geq 15$, in the photometric redshift range $z\in [0.1, 0.6]$, comparing our measurements with theoretical models, in the framework of the $\Lambda$-Cold Dark Matter cosmology. We perform a Monte Carlo Markov Chain analysis to constrain the cosmological parameters $\Omega_{\mathrm{m}}$, $\sigma_8$ and the structure growth parameter $S_8\equiv\sigma_8 \sqrt{\Omega_{\mathrm{m}}/0.3}$. We adopt Gaussian priors on the parameters of the mass-richness relation, based on the posterior distributions derived from a previous joint analysis of cluster counts and weak lensing mass measurements carried out with the same catalogue. From the angular correlation function, we obtain $\Omega_{\mathrm{m}}=0.32^{+0.05}_{-0.04}$, $\sigma_8=0.77^{+0.13}_{-0.09}$ and $S_8=0.80^{+0.08}_{-0.06}$, in agreement, within $1\sigma$, with 3D clustering result based on the same cluster sample and with existing complementary studies on other datasets. For the angular power spectrum, we derive statistically consistent results, in particular $\Omega_{\mathrm{m}}=0.24^{+0.05}_{-0.04}$ and $S_8=0.93^{+0.11}_{-0.12}$, while the constraint on $\sigma_8$ alone is weaker with respect to the one provided by the angular correlation function, $\sigma_8=1.01^{+0.25}_{-0.17}$. Our results show that the 2D clustering from photometric cluster surveys can provide competitive cosmological constraints with respect to the full 3D clustering statistics, and can be successfully applied to ongoing and forthcoming spectro/photometric surveys.Comment: 14 pages, 9 figures. Submitted to Astronomy & Astrophysics (A&A

AMICO galaxy clusters in KiDS-DR3: cosmological constraints from counts and stacked weak-lensing

We present a cosmological analysis of abundances and stacked weak-lensing profiles of galaxy clusters, exploiting the AMICO KiDS-DR3 catalogue. The sample consists of 3652 galaxy clusters with intrinsic richness $\lambda^*\geq20$, over an effective area of 377 deg$^2$, in the redshift range $z\in[0.1,\,0.6]$. We quantified the purity and completeness of the sample through simulations. The statistical analysis has been performed by simultaneously modelling the comoving number density of galaxy clusters and the scaling relation between the intrinsic richnesses and the cluster masses, assessed through a stacked weak-lensing profile modelling. The fluctuations of the matter background density, caused by super-survey modes, have been taken into account in the likelihood. Assuming a flat $\Lambda$CDM model, we constrained $\Omega_{\rm m}$, $\sigma_8$, $S_8 \equiv \sigma_8(\Omega_{\rm m}/0.3)^{0.5}$, and the parameters of the mass-richness scaling relation. We obtained $\Omega_{\rm m}=0.24^{+0.03}_{-0.04}$, $\sigma_8=0.86^{+0.07}_{-0.07}$, $S_8=0.78^{+0.04}_{-0.04}$. The constraint on $S_8$ is consistent within 1$\sigma$ with the results from WMAP and Planck. Furthermore, we got constraints on the cluster mass scaling relation in agreement with those obtained from a previous weak-lensing only analysis.Comment: 12 pages, 7 figures, 2 tables. Accepted by A&

Euclid Preparation. XXXVII. Galaxy colour selections with Euclid and ground photometry for cluster weak-lensing analyses

We derived galaxy colour selections from Euclid and ground-based photometry, aiming to accurately define background galaxy samples in cluster weak-lensing analyses. Given any set of photometric bands, we developed a method for the calibration of optimal galaxy colour selections that maximises the selection completeness, given a threshold on purity. We calibrated galaxy selections using simulated ground-based $griz$ and Euclid $Y_{\rm E}J_{\rm E}H_{\rm E}$ photometry. Both selections produce a purity higher than 97%. The $griz$ selection completeness ranges from 30% to 84% in the lens redshift range $z_{\rm l}\in[0.2,0.8]$. With the full $grizY_{\rm E}J_{\rm E}H_{\rm E}$ selection, the completeness improves by up to $25$ percentage points, and the $z_{\rm l}$ range extends up to $z_{\rm l}=1.5$. The calibrated colour selections are stable to changes in the sample limiting magnitudes and redshift, and the selection based on $griz$ bands provides excellent results on real external datasets. The $griz$ selection is also purer at high redshift and more complete at low redshift compared to colour selections found in the literature. We find excellent agreement in terms of purity and completeness between the analysis of an independent, simulated Euclid galaxy catalogue and our calibration sample, except for galaxies at high redshifts, for which we obtain up to 50 percent points higher completeness. The combination of colour and photo-$z$ selections applied to simulated Euclid data yields up to 95% completeness, while the purity decreases down to 92% at high $z_{\rm l}$. We show that the calibrated colour selections provide robust results even when observations from a single band are missing from the ground-based data. Finally, we show that colour selections do not disrupt the shear calibration for stage III surveys.Comment: 20 pages, 13 figures. Published by A&

Surface features and thermal stability of mesoporous Fe doped geoinspired synthetic chrysotile nanotubes

Synthetic mesoporous Fe doped geoinspired nanotubes have been utilized to evaluate the modification of the surface composition, morphology charge distribution and thermal stability as functions of the Fe doping extent and Fe prevalent substitution into the octahedral or tetrahedral sites. FTIR-ATR spectroscopy analysis has allowed to highlight the chrysotile structure modification by the Fe substitution to Mg or Si and to underline clearly the crucial role of the Fe doping in the octahedral sheet in modifying chrysotile structure and morphology. XPS analysis, f-potentials and porosity characterization have allowed to define the propriety of the chrysotile surface structure when iron replaces Mg in octahedral or Si in tetrahedral sites. DTA analysis has allowed to relate the effect of Fe doping on the chemical–physical characteristics of both synthetic and mineral chrysotile. We have observed that the simultaneous decrease in dehydroxylation and recrystallization temperature occurs when the Fe increases on surface and this is due to the increased substitution of Fe in octahedron. The results highlight the relevance to estimate the health hazard of the natural asbestos fibres by valuating the role of Fe surface throughout the use of geoinspired chrysotile synthesised under controlled stoichiometry and structure utilizing it as a selected reference standard

The Iron-Related Molecular Toxicity Mechanism of Synthetic Asbestos Nanofibres: A Model Study for High-Aspect-Ratio Nanoparticles

Asbestos shares with carbon nanotubes some morphological and physico-chemical features. An asbestos-like behaviour has been recently reported by some authors, though the mechanism of toxicity may be very different. To identify at the atomic level the source of toxicity in asbestos, the effect of progressive iron loading on a synthetic iron-free model nanofibre previously found non-toxic in cellular tests was studied. A set of five synthetic chrysotile nanofibres [(Mg,Fe)3(Si2O5)(OH)4] has been prepared with Fe ranging from 0 to 1.78\u2005wt\u2009%. The relationship between fibre-induced free-radical generation and the physico-chemical characteristics of iron active sites was investigated with spin-trapping techniques on an aqueous suspension of the fibres and M\uf6ssbauer and EPR spectroscopies on the solids, respectively. The fully iron-free fibre was inert, whereas radical activity arose with even the smallest amount of iron. Surprisingly, such activity decreased upon increasing iron loading. M\uf6ssbauer and EPR revealed isolated iron ions in octahedral sites that undergo both axial and rhombic distortion and the occurrence of aggregated iron ions and/or extra-framework clustering. The isolated ions largely prevailed at the lowest loadings. Upon increasing the loading, the amount of isolated iron was reduced and the aggregation increased. A linear relationship between the formation of carbon-centred radicals and the amount of rhombic-distorted isolated iron sites was found. Even the smallest iron contamination imparts radical reactivity, hence toxicity, to any chrysotile outcrop, thereby discouraging the search for non-toxic chrysotile. The use of model solids that only differ in one property at a time appears to be the most successful approach for a molecular understanding of the physico-chemical determinants of toxicity. Such findings could also be useful in the design of safer nanofibres

Mass bias and cosmological constraints from

Aims. We analysed the 3D clustering of the Planck sample of Sunyaev–Zeldovich (SZ) selected galaxy clusters, focusing on the redshift-space two-point correlation function (2PCF). We compared our measurements to theoretical predictions of the standard Λ cold dark matter (ΛCDM) cosmological model, deriving an estimate of the Planck mass bias, bSZ, and cosmological parameters. Methods. We measured the 2PCF of the sample in the cluster-centric radial range r ∈ [10, 150] h−1 Mpc, considering 920 galaxy clusters with redshift z ≤ 0.8. A Markov chain Monte Carlo analysis was performed to constrain bSZ, assuming priors on cosmological parameters from Planck cosmic microwave background (CMB) results. We also adopted priors on bSZ from external data sets to constrain the cosmological parameters Ωm and σ8. Results. We obtained $(1-b_{\mathrm{SZ}})=0.62^{+0.14}_{-0.11}$, which agrees with the value required to reconcile primary CMB and cluster count observations. By adopting priors on (1 − bSZ) from external data sets, we derived results on Ωm that fully agree and are competitive, in terms of uncertainties, with those derived from cluster counts. This confirms the importance of including clustering in cosmological studies in order to fully exploit the information from galaxy cluster statistics. On the other hand, we found that σ8 is not constrained