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Detection of TeV rays from the Cygnus Region with Milagro

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Detection of TeV rays from the Cygnus Region with Milagro – PowerPoint PPT presentation

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Title: Detection of TeV rays from the Cygnus Region with Milagro


1
Detection of TeV ?-rays from the Cygnus Region
with Milagro
  • Aous Abdo
  • for the Milagro Collaboration
  • May 11, 2006, Santa Fe, NM

2
The 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

5
Background 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
6
A4 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
7
TeV 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)

8
TeV 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

9
A 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)

10
Cygnus Region
Canadian Galactic Plane Survey - Far IR
11
Cygnus 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
12
Conclusions
  • 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.
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