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Milagro-EGRET Correlation

MGRO J2031+41 (GeV J2035+4214). MGRO J2005+33 (high matter density?). MGRO J2226+60 (Boomerang PWN). MGRO J2019+37 (GeV J2020+3658). MGRO J2044+36 (no counterpart). MGRO J1908+06 (GeV J1907+0557). MGRO J2031+36 (extension of J2019?). MGRO J0634+17 (Geminga). Crab nebula.

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Milagro-EGRET Correlation

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  1. MGRO J2031+41 (GeV J2035+4214) MGRO J2005+33 (high matter density?) MGRO J2226+60 (Boomerang PWN) MGRO J2019+37 (GeV J2020+3658) MGRO J2044+36 (no counterpart) MGRO J1908+06 (GeV J1907+0557) MGRO J2031+36 (extension of J2019?) MGRO J0634+17 (Geminga) Crab nebula Milagro-EGRET Correlation

  2. Milagro/EGRET Overlap Probability • 14 EGRET sources in the GeV catalog (in this region of the Galaxy) • N(=6,7,8?) Milagro sources • 5 EGRET sources are “close” to Milagro candidates • “close” = falls within a 3x3 bin drawn around each Milagro candidate • What is the probability of this? • Monte Carlo • Analytic (not quite correct)

  3. Monte Carlo 20 190

  4. 8 Milagro Sources 8 x 10-6 chance that 5 of 8 overlap w/EGRET

  5. 6 Milagro Sources 2 x 10-6 chance that 5 of 6 overlap w/EGRET

  6. Analytic Method • Place 8 (6?) Milagro sources with 3x3 degree bins around each within a 190x20 degree region. • Throw 1 EGRET source • Probability (P1) to land in a Milagro region • Nsources x Bin Area/ Regional Area • 8 x 9 / (190x20) = 0.019 • 6 x 9 / (190x20) = 0.014

  7. Combinatorics • 14 Choose j (= # overlaps) possible combinations (not quite correct, there are more). • Then sum to get probability of N overlaps or more

  8. 3 4 5 6 7 8 N of 8 Milagro Sources Overlap 5 x 10-6 chance that 5 of 8 overlap w/EGRET

  9. N of 6 Milagro Sources Overlap 3 4 5 6 1 x 10-6 chance that 5 of 6 overlap w/EGRET

  10. MGRO J2019+37 MGRO J2032+41 MGRO J2005+33 MGRO J2031+36 MGRO J2044+36 Diffuse vs. Point Source

  11. Post Trial Significance 0. 4.2% 0. 30% 0. 9.e-3 4.2e-7 .003 30% Assume 150,000 trials

  12. Conclusion • We need to know what we are claiming to see • We need to know what we mean by “close to” • Given my assumptions overlap probability (5 of 8 Milagro candidates) is 8 x 10-6 (4.3 ) • We should incorporate diffuse model in source search • We should be careful about claiming discovery with marginal significance and a posteriori hypotheses

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