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2011, 10th AprilIII Fermi symposium1
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Needlets definition NPW (2006)
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Results for ground-based telescopes with large field of view 2011, May16 SIMULATION DETAILS: Sky map filled with all the TeV sources in the field of view of ARGO intermediate scale CRs anisotropies as observed by ARGO isotropic CRs flux according to Horandel The effect of the atmosphere, as well as that of the detector (efficiency, exposure and so on…) have been properly accounted for. 1.2X10 11 events to reproduce 3 years of data acquisition. No selection cuts applied. celestial coordinates (r.a. and dec.) The signals lay on different angular scales, then we expect to observe them at different needlet orders.
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The background-subtracted map is dominated by high frequency fluctuations. Needlet transform 2011, May17 Point sources visible at j=8-10 Intermediate scale anisotropies visible at j=4-7
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Estimation of the r.m.s. 18 The estimation of the r.m.s of each coefficient is easily obtained by MC simulation of the background. 1000 background samples full needlet transform for each sample
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Managing the transform coefficients 2011, May19 Point source detection in the needlet space! You can use the estimation of the r.m.s. of the beta coefficients to get the significance of every point at every scale. Point source detection in the needlet space! soft thresholding You can make the antitransform using only significant coefficients (e.g. “soft thresholding”). Weight function Signals well separated even when overlap each other!
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Simulation of the application to Fermi 2011, May20 Point sources from the LAT 1-year Point Source Catalog (1451 sources) Diffuse Galactic background (gll_iem_v02.fit) Diffuse extragalactic isotropic background (spectral index -2.4) Events selected within 105° zenith angle Energy 1-100 GeV Simulated exposure time: 3.16X10 6 secs (1 year) Instrument response functions from P6_V3_DIFFUSE Details of the simulation:
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Beta coefficients of the Fermi sky-map 2011, May21 Diffuse signals lay at lower scales very good estimation if the stronger sources are masked (very standard technique in CMB data analysis). Only point sources are visible at high needlet orders (diffuse back/foreground simply lives on other angular scales)
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A zoom of the Cygnus region 2011, May22 Soft thresholding Soft thresholding: we use only beta coefficients larger than 5 r.m.s. (r.m.s. roughly estimated). r.m.s. estimation region
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Soft thresholding application 2011, May23 r.m.s. estimation region Fermi 1FGL less significant source
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