Download - Update on the Intermediate-Scale Structure
Update on the Intermediate-Scale Structure
Gary Walker
Los Alamos National Laboratory
Introduction
•Intermediate-scale structure seen in map with no gamma/hadron cut
•Also visible in x2, A4 maps
Significance Map: No g/h cut, 5.1° bin
Significance Map: A4 weighted analysis, Gaussian smoothing
Seasonal Effect?
•Split data into seasons
•Same structure seen in all of them
Brian’s Anisotropy
•Simulations indicate that Brian’s anisotropy will cause a mis-estimation of the background•However, this does not seem to be the cause of the structures at RA≈70° and ra≈130°
Declination Slice
Full Dataset (Total Int Duration = 2150 days)
10° < Dec < 20°, 1° Binning in RA (Independent 10° x 1° Bins)
Red = SkyRed = Sky
Black = Bkg
Black = Bkg
•Region at ra=70° does not appear to be an underestimation of the background
Compare with Tibet Anisotropy
•Similarity seen with Tibet anisotropy ( > 4TeV, 1997-2005), especially at ra=70°
What is it?
•Brightest spot (around ra=70°) in no g/h cut map: Excess = 165 K, Bkg = 220 MS/B = (7.5 ± 0.7) x 10-4
•Brightest spot (around ra=70°) in A4>1 map: Excess = 34.4 K, Bkg = 19.7 MS/B = (17.5 ± 2.5) x 10-4 This is inconsistent by 3.8σ
•A4 for a steep spectrum gamma source will look like background
•A4 for a hard spectrum proton source will look more gamma-like
nTop > 150 CutnFit > 20, No Gamma/Hadron Cut
nTop > 150, No Gamma/Hadron Cut
•Bottom map has 20% of the number of events in the top map•Based only on statistics, significance should drop to ~4.5σ
Summary / What to do next?
•The features at ra≈70° and ra≈135° appear to be real•Suggestions for further tests?
•Brian’s anisotropy doesn’t appear to be the cause, but may be causing some mis-estimation of the background – use simulation to correct
•Use gamma and proton simulations to quantify what kind of spectrum will produce the observed A4 and nTop behavior
•Any other suggestions?