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?