Title: Detection of TeV rays from the Cygnus Region with Milagro
1Detection of TeV ?-rays from the Cygnus Region
with Milagro
- Aous Abdo
- for the Milagro Collaboration
- May 11, 2006, Santa Fe, NM
2The Milagro TeV ?-ray Detector
- Water Cherenkov Detector
- 2 steradian field of view
- 1.7 kHz data rate
- 898 detectors
- 450(t) / 273(b) in pond
- 175 water tanks
- gt 90 duty cycle
- 0.6 - 0.3 Degree point spread function
- 0.1 100 TeV energy range
Milagro Cross Section Schematic
3(No Transcript)
4 Background Rejection in Milagro
- Differences between Hadron- and Gamma-ray-
initiated EAS - Hadronic EAS contain many more muons than those
for gamma ray EAS - Hadronic EAS result in a bright, compact clusters
of light in the muon layer - Gamma EAS illuminate the muon layer uniformly,
with small hits
5Background Rejection (Contd)
- Parameterize clumpiness of the bottom layer
hits - Compactness
- Require C gt 2.5
- 50 gammas 10 hadrons
- Sensitivity improved by 1.6
- Require A4 gt 3.0
- 20 gammas 1 hadrons
- Sensitivity further improved by 1.4
mxPE maximum PEs in bottom layer PMT nb2
bottom layer PMTs with 2 PEs or more fTop
fraction of hit PMTs in Top layer fOut
fraction of hit PMTs in Outriggers nFit PMTs
used in the angle reconstruction
6A4 Weighting Analysis on the Crab Nebula
Combine A4 with the weighting Analysis on 5 Years
of Data
A4 gt 3.0 , nFit gt 40
A4 gt 7.0 , nFit gt 40
Weight each event by Expected S/B
Excess Signal 3397 Background 221,263 S/B
1.5 10-2
Excess Signal 519 Background 11726 S/B 5.0
10-2
7TeV Sky Map Survey (Milagro 2003)
Mrk 421
Crab Nebula
- gt5 ? detections of Crab and Mrk 421 (AGN)
- 9 other points gt 4 ? (consistent with background)
8TeV Sky Map Survey 2006
Preliminary
- Crab Nebula 14 ?
- Galactic Ridge clearly visible
- Cygnus Region 12 ?
- A4 New Gamma-Hadron Separation Variable
- Weighting Analysis
- 5 Years of data, 2 with outriggers used in event
reconstruction providing much - better sensitivity
- Outriggers keep high energy gammas
9A Closer Look at the Galactic Plane
Preliminary
Preliminary
- GP diffuse excess clearly
- visible from l25O to l90O.
- Cygnus Region shows
- extended excess
- FCygnus 2 x Fcrab 120 square degrees l
(65,85), b (-3,3)
10Cygnus Region
Canadian Galactic Plane Survey - Far IR
11Cygnus Region Spatial Morphology
- Crosses are EGRET sources
- Contours are EGRET diffuse model
- TeV/matter correlation good in Galactic latitude
- Brightest TeV Region
- Coincident with 2 EGRET sources
(unidentified)3EG J201636573EG J20213716 - Analysis in progress
Preliminary
12Conclusions
- Milagro has proven the capabilities and
importance of surveying the TeV sky with a large
field of view, high duty cycle observatory. - New analysis has lead to significant improvements
in Milagro's Capabilities - All-sky survey has lead to significant
discoveries - Diffuse TeV gamma ray emission from the Galactic
plane - Extended source in the Cygnus region at 12 sigma
in TeV gamma rays - Diffuse emission from Cygnus region
- Given the diffuse nature of the detected region,
the Cygnus Region is the most luminous source
of TeV gamma rays in the northern sky - Milagro is a 1st generation water Cherenkov
detector and with the miniHAWC, 2nd generation
detector, major improvements in sensitivity are
possible for moderate costs.