97 research outputs found

    On the signature of z0.6z\sim 0.6 superclusters and voids in the Integrated Sachs-Wolfe effect

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    Through a large ensemble of Gaussian realisations and a suite of large-volume N-body simulations, we show that in a standard LCDM scenario, supervoids and superclusters in the redshift range z[0.4,0.7]z\in[0.4,0.7] should leave a {\em small} signature on the ISW effect of the order 2μ\sim 2 \muK. We perform aperture photometry on WMAP data, centred on such superstructures identified from SDSS LRGs, and find amplitudes at the level of 8 -- 11μ \muK -- thus confirming the earlier work of Granett et al 2008. If we focus on apertures of the size \sim3.6\degr, then our realisations indicate that LCDM is discrepant at the level of 4σ\sim4 \sigma. If we combine all aperture scales considered, ranging from 1\degr--20\degr, then the discrepancy becomes 2σ\sim2\sigma, and it further lowers to 0.6σ\sim 0.6 \sigma if only 30 superstructures are considered in the analysis (being compatible with no ISW signatures at 1.3σ1.3\sigma in this case). Full-sky ISW maps generated from our N-body simulations show that this discrepancy cannot be alleviated by appealing to Rees-Sciama mechanisms, since their impact on the scales probed by our filters is negligible. We perform a series of tests on the WMAP data for systematics. We check for foreground contaminants and show that the signal does not display the correct dependence on the aperture size expected for a residual foreground tracing the density field. The signal also proves robust against rotation tests of the CMB maps, and seems to be spatially associated to the angular positions of the supervoids and superclusters. We explore whether the signal can be explained by the presence of primordial non-Gaussianities of the local type. We show that for models with \FNL=\pm100, whilst there is a change in the pattern of temperature anisotropies, all amplitude shifts are well below <1μ<1\muK.Comment: 14 pages, 9 figures, matches accepted version in MNRA

    The clustering of merging star-forming haloes: dust emission as high frequency arcminute CMB foreground

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    Future observations of CMB anisotropies will be able to probe high multipole regions of the angular power spectrum, corresponding to a resolution of a few arcminutes. Dust emission from merging haloes is one of the foregrounds that will affect such very small scales. We estimate the contribution to CMB angular fluctuations from objects that are bright in the sub-millimeter band due to intense star formation bursts following merging episodes. We base our approach on the Lacey-Cole merger model and on the Kennicutt relation which connects the star formation rate in galaxies with their infrared luminosity. We set the free parameters of the model in order to not exceed the SCUBA source counts, the Madau plot of star formation rate in the universe and COBE/FIRAS data on the intensity of the sub-millimeter cosmic background radiation. We show that the angular power spectrum arising from the distribution of such star-forming haloes will be one of the most significant foregrounds in the high frequency channels of future CMB experiments, such as PLANCK, ACT and SPT. The correlation term, due to the clustering of multiple haloes at redshift z~2-6, is dominant in the broad range of angular scales 200<l<3000. Poisson fluctuations due to bright sub-millimeter sources are more important at higher l, but since they are generated from the bright sources, such contribution could be strongly reduced if bright sources are excised from the sky maps. The contribution of the correlation term to the angular power spectrum depends strongly on the redshift evolution of the escape fraction of UV photons and the resulting temperature of the dust. The measurement of this signal will therefore give important information about galaxies in the early stage of their evolution.Comment: 18 pages, 16 figures. Accepted by Astronomy & Astrophysic

    Galaxy Clusters as mirrors of the distant Universe. Implications for the kSZ and ISW effects

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    It is well known that Thomson scattering of CMB photons in galaxy clusters introduces new anisotropies in the CMB radiation field, but however little attention is payed to the fraction of CMB photons that are scattered off the line of sight, causing a slight blurring of the CMB anisotropies present at the moment of scattering. In this work we study this {\it blurring} effect, and find that it has a non-negligible impact on estimations of the kinetic Sunyaev-Zel'dovich (kSZ) effect: it induces a 10% correction in 20-40% of the clusters/groups, and a 100% correction in 5\sim 5% of the clusters in an ideal (noiseless) experiment. We explore the possibility of using this blurring term to probe the CMB anisotropy field at different epochs in our Universe. In particular, we study the required precision in the removal of the kSZ that enables detecting the blurring term τTδT/T0-\tau_T \delta T / T_0 in galaxy cluster populations placed at different redshift shells. By mapping this term in those shells, we would provide a tomographic probe for the growth of the Integrated Sachs Wolfe effect (ISW) during the late evolutionary stages of the Universe. We find that the required precision of the cluster peculiar velocity removal is of the order of 100 -- 200 km s1^{-1} in the redshift range 0.2 -- 0.8, after assuming that all clusters more massive than 1014^{14} h1^{-1} M_{\odot} are observable. These errors are comparable to the total expected linear line of sight velocity dispersion for clusters in WMAPV cosmogony, and correspond to a residual level of roughly 900 -- 1800 τTμ\tau_T \muK per cluster, including all types of contaminants and systematics. Were this precision requirement achieved, then independent constraints on the intrinsic cosmological dipole would be simultaneously provided.Comment: Notation clarified and typos and errors corrected in eqs.(2-4

    Envisioning patient safety in Telehealth: a research perspective

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    This article explores the need for research into patient safety in large-scale Telehealth systems faced with the perspective of its development extended to healthcare systems. Telehealth systems give rise to significant advantages in improving the quality of healthcare services as well as bringing about the possibility of new types of risk. A theoretical framework is proposed for patient safety for its approach as an emerging property in complex socio-technical systems (CSTS) and their modelling in layers. As regards this framework, the differential characteristic Telehealth elements of the system have been identified, with a greater emphasis on the level of Telehealth system and its typical subsystems. The bases of the analysis are based on references in the literature and the experience accumulated by the researchers in the area. In particular, a case describing an example of Telehealth to control patients undergoing treatment with oral anticoagulants is used. As a result, a series of areas of research into and topics regarding Telehealth patient safety are proposed to cover the detectable gaps. Both the theoretical and practical implications of the study are discussed and future perspectives are reflected on.This research has been partially supported by grants FISPI09-90110 ‘Innovation Platform in new services based on telemedicine and e-health for chronic and dependent patients -PITES’ from the Ministry of Health & Consumer Affairs; and FISPI13-00508 ‘Innovation platform in new services based on Telemedicine and e- Health: definition, design and development of tools for interoperability, patient safety and support to decision (PITES-ISA)’ from the Ministry of Economy and Competitiveness (Secretary of State of Research, Development and Innovation). The funders had no role in the study, decision to publish, or drafting of the manuscript.S