A Survey of EGRET GeV Sources Chuan Chen University of California, Irvine EGRET GeV Catalog Trials Factor Simulation Milagro U.L. and EGRET Flux

Milagro Collaboration Meeting, 04/20/2007 EGRET GeV Catalog # of EGRET gamma-ray sources detected > 1 GeV is 57 (Lamb & Macomb, ApJ 488:872, 1997) 46 are high (>5.0 σ), 6 are low (4.5 σ – 5.0 σ), 5 are very low significance sources (4.0 σ – 4.5 σ). Milagro field of view (-5o < d < 70o) contains 32 25 high, 5 low and 2 very low significance GeV sources 14 are in the Galactic plane ( -10o < l < 10o) Milagro data is searched for brightest location within 1.0 degree radius of the GeV sources Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Searching Results for Some Sources Source Name 1 Hottest spot Location (l, b) Pre-trials Sigma 2 Post-trials Probability Identification GEV J0534+2159 184.6, -5.6 15.54 2.92E-52 2EG J0534+2158, Crab GEV J2020+3658 75.1, 0.1 10.92 1.45E-25 2EG J2019+3719 GEV J1907+0557 40.7, -1.1 8.55 1.93E-15   GEV J2035+4214 80.5, 1.1 6.89 7.29E-10 GEV J1104+3809 179.0, 65.1 6.66 3.30E-09 2EG J1104+3812, Mkn 421 GEV J2026+4124 80.2, 1.3 6.55 6.66E-09 GEV J0634+1746 194.9, 4.5 4.99 3.86E-05 2EG J0633+1745, Geminga GEV J2020+4023 78.5, 1.3 4.48 0.00038 2EG J2020+4026, possibly γ Cygni SNR GEV J2227+6101 106.1, 2.8 2EG J2227+6122 GEV J1856+0115 33.5, -0.1 4.26 0.00095 2EG J1857+0118, possible W44 SNR GEV J0633+0645 204.8, -0.3 3.17 0.04 Possibly Monoceros SNR 3 1 Position with maximum sigma in each searching region 2 Trials factor are determined by Monte Calor 3 They are one source in Milagro Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Simulation of Trials Factor Using Bin Smoothed Maps Bins are correlated since we use Gaussian smoothed maps. Using the total number of bins in the searching region will overestimate the trials factor. Simulate number of trials factor for different significant sources Trials Factor Significance Nm is the number of maps with the maximum significance greater than n sigmas in the searching region. Nt is the total maps (1 billion) Pn is the probability greater than n sigmas. (e.g. P3 = 0.0013499) NTrials is the number of trials Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Trials Factor using Gaussian Smoothed Maps From Crab fit we get psf is 0.73 +/- 0.06. I used 0.6 degrees as the sigma of psf and simulated 20 million maps. Sigma of psf equals 0.6 is roughly the same as bin size equals 1.7 degrees. I didn’t find the reason of the disagreement Trials Factor Significance Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Trials Factor for the Galactic Plane Sources Simulated 200,000 galactic planes (l[0°,180°], b[-5°, 5°]) Using two different bin sizes (1.7 and 2.9 degrees) Can be scaled to the real galactic plane region we used Total number of bins in the simulated galactic plane (180,000) Trials Factor Significance Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Milagro Collaboration Meeting, 04/20/2007 Milagro Distribution of Post-trials Probabilities’ for 32 EGRET GeV Sources 1.5 degree binning size is roughly the equivalent binning size for Gaussian smoothed method we used. Fitting the plot on previous page (2-5 sigmas and extrapolate to higher significance) to get the trials factors for different significant sources. # of EGRET GeV Sources post-trial probability cut for the table Post-trial Probability Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Milagro u.l. vs EGRET GeV Flux E2 dN/dE @ 20 TeV Milagro measurements and upper limit (ergs/cm2 sec) Red is Crab Green is Geminga Blues are in the galactic plane paper Purples are u.l. The differential photon spectra of all EGRET GeV sources between 1 GeV and 20 TeV is steeper than E-2 Equal energy flux E2 dN/dE @ 1 GeV EGRET measurements (ergs/cm2 sec) Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Milagro u.l. vs EGRET extrapolation to 20 TeV E2 dN/dE @ 20 TeV Milagro measurements and upper limit (ergs/cm2 sec) Equal energy flux Red is Crab Green is Geminga Blues are in the galactic plane paper Purples are u.l. Spectra are taken from the 3rd EGRET catalog of high-energy gamma-ray sources The differential photon spectra of many EGRET GeV sources steepens above 1 GeV E2 dN/dE @ 20 TeV EGRET extrapolation (ergs/cm2 sec) Chuan Chen Milagro Collaboration Meeting, 04/20/2007

Milagro Collaboration Meeting, 04/20/2007 Conclusion 32 of 57 EGRET gamma-ray sources detected > 1 GeV are in Milagro field of view 14 are in the Galactic plane 11 (6) of them with pre-trial significance > 3 (5) sigma and post-trial significance > 2 (4) sigmas Upper limits are placed on the TeV flux of EGRET GeV sources I will calculate the flux for the GeV sources with pre-trial significance greater than 3 sigmas Chuan Chen Milagro Collaboration Meeting, 04/20/2007