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

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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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