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تسجيل مستخدم جديدGalaxy Cluster Contribution to the Diffuse Extragalactic Ultraviolet Background
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The diffuse ultraviolet background radiation has been mapped over most of the sky with 2arcmin resolution using data from the textit{GALEX} survey. We utilize this map to study the correlation between the UV background and clusters of galaxies discovered via the Sunyaev-Zeldovich effect in the textit{Planck} survey. We use only high Galactic latitude ($|b| > 60^{circ} $) galaxy clusters to avoid contamination by Galactic foregrounds, and we only analyze clusters with a measured redshift. This leaves us with a sample of 142 clusters over the redshift range $0.02 leq z leq 0.72$, which we further subdivide into four redshift bins. In analysing our stacked samples binned by redshift, we find evidence for a central excess of UV background light compared to local backgrounds for clusters with $z<0.3$. We then stacked these $z<0.3$ clusters to find a statistically significant excess of $12 pm 2.3$ photon cm$^{-2}$ s${-1}$ sr$^{-1}$ AA $^{-1}$ over the median of $sim 380$ photon cm$^{-2}$ s${-1}$ sr$^{-1}$ AA $^{-1}$ measured around random blank fields. We measure the stacked radial profile of these clusters, and find that the excess UV radiation decays to the level of the background at a radius of $sim 1$ Mpc, roughly consistent with the maximum radial extent of the clusters. Analysis of possible physical processes contributing to the excess UV brightness indicates that non-thermal emission from relativistic electrons in the intracluster medium and faint, unresolved UV emission from cluster member galaxies and intracluster light are likely the dominant contributors.
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CONTEXT: The Virgo direction has been observed at many wavelengths in the recent years, in particular in the ultraviolet with GALEX. The far ultraviolet (FUV) diffuse light detected by GALEX bears interesting information on the large scale distributi
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