Gamma-ray Mapping of the Interstellar Medium and Cosmic Rays in the Galactic Plane with GLAST
Yasushi Fukazawa1, T. Kamae1,2, T. Ohsugi1, T. Mizuno1,S. Yoshida1, K. Hirano1, M. Ozaki3, and GLAST team
(1:Hiroshima University, 2:SLAC, 3:ISAS)
GLAST, the next gamma-ray satellite, will be launchedin 2005 under USA, Japan, Italy, France, and so on. Newt echnologies, such as silicon-strip detectors developed inHiroshima University, enable us to obtain a much imporoved capabilities for gamma-ray observations; 50 times as good as sensitivity as EGRET, good source location down to a few arcmins, and a wider fieldof view with 20% of the whole sky. Thanks to these characteristics, GLAST will detect more than 10,000 objects. Together with Gamma-ray bursts, Pulsars, BLAZARs, SNRs, Dark matters, the mapping of the Galactic diffuse gamma-ray emission is one of key sciences. This enables us to obtain the distribution of the interstellar medium and cosmic rays in the Galactic plane, especially of protons. We are now developing not only FM silicon-strip detectors but also instrumental simulators which will helpus to perform such complex analyses.
SAS-2
OSO-3
COS-B
EGRET(CGRO)
GLAST
1991-2000
1972-73
1967
1975-1982
2005-
Increase of number of detected objects
GLAST will detect >10,000gamma-ray sources. Various kinds of astronomical objects can be observed, and thus GLAST will open a new era ofgamma-ray astronomy.
EGRET GLAST
1
9cm
Silicon-StripDetector (FM)
Developed by HiroshimaUniv. and HPK (Japan)
New Technology
PD readout
Anti-Coincidence Detector (ACD)
CsI-Array Calorimeter (CAL)
Plastic-Scinti+ PMT
4x4 array of 4x4 array of identical towersidentical towers
Si -Pb Tracker (TKR)
Gamma-ray
Silicon-Strip Detector
CsI Calorimeter
2
EGRET GLASTEnergy Band 30MeV--10GeV 20MeV--100GeVField of View 0.5sr 2.4sr (20% of 4π)Effective Area 1,500cm2 11,000cm2Energy Resolution 10% 10%Dead time per 1 event 100ms 20μsSource Location 5--30arcmin 0.5--5 arcminSensitivity ~ 1×10-7cm-2s-1 ~ 1×10-7cm-2s-1(1day) ~ 2×10-9cm-2s-
1(2years)Number of Detected objects 271 >10000Weight 1820kg 2560kgOrbit(28.5O incl.) 350km 550kmLife time 9years >5yesrs
Basic Performance of GLAST
EGRET
GLAST
3
GLAST is also important as All-sky Monitor
1orbit
1 day
100 sec Wide field of view ( 20% of the whole sky )can cover 85% of the whole sky in 1orbit(100min)200 Gamma-ray Bursts per year
Day-scale light curve willbe available for all 3EG sources + 80 new sources
104 sources in 2 years
GLAST and MAXI (Japanese X-ray all-sky monitor, 2005-) cooperation will be important.
Sky covering
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Pi-0 decay (cosmic ray p) * (interstellar gas)
IC (cosmic ray e) * (interstellar photon)Radio-synchrotron (cosmic ray e) * (interstellar B)
100MeV 100GeV
Bremss(e)
π decay(p)
InverseCompton(e)
One of key sciences of GLAST is the Diffuse Gamma-Ray Emission along the Galactic Plane.
We can study energy density and distribution of Cosmic-ray Proton, Electron, and Gas (and B), separately,and study the Galactic Structure and Formation in terms of Energetics !
Bremss (cosmic ray e) * (interstellar gas)
0COS-B (Mayer-Hasselwander et al. 1982)
Gamma-ray is emitted by the interaction between the interstellar medium and cosmic-rays.
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Koyama et al. 1995 Tanimori et al. 1998
EGRET image (left) and GLAST Simulation of the Gamma-Cyg wheresupernova remnant and molecular cloud are thought to be interacting.
Evidences of particle acceleraton in thesupernova remnant SN1006.
Identify the cosmic-ray acceleration sites.
Pulsar nubula
From top, 408MHz ( Synchrotron )、 21cm(H1) 、CO(H2) 、 FIR ( dust,HI )、 NIR ・ optical(stars) 、X -ray ( hot gas )
Multi-wavelength images of the Galactic plane
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LMC (EGRET detected)
Starburst Galacy: M82
Clusters of galaxies
Simulated gamma-ray spectrum of the Galactic plane with GLAST
Orion
EGRET image of thegiant molecular cloud
SMC
Digel et al. 1999
Non-biasing survey of the interstellar gas and cosmic-ray protons and electrons!
GLAST simulation
M31
Comparison of cosmic-ray density with other galaxies
Combined with other wavelength data, we can obtain the distribition of various Galactic materials.
Galaxy radiation simulator
(2x2degre2)
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Extended emission Complex Detector ResponsesScanning observation
But,
Forward method anlysis with full-detecor and BGD simulator is valuable and efficient.
Gamma-ray sky map model
BGD Simulator
Detector Simulator
Data Reduction
Simulated Data
Comparison (Fitting)
Feed-back
BGD model
Real Data
We are now developing …..
Protons Electrons
Detector simulator (Geant4)Cosmic-ray generator for BGD simulation
These are at first applied to the Balloonflight experiments (see postar p210).
Further works...Extention to FM model, include He, e+, gamma-ray etc.Tuning through calibrations, study of BGD rejection
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