1
GeV Gamma Ray Astronomy in the GLAST Era
Neil Gehrels
June 26, 2000
2
Recent Development in U.S.
Astronomy and Astrophysics in the New MillenniumNRC 10-year Report
Table 1.1 Prioritized Initiatives and Estimated Federal Costs for the Decade 2000-2010.
Ground BasedCost($M)
Space BasedCost($M)
Major Initiatives
Giant Segmented-Mirror Telescope (GSMT) 350 Next Generation Space Telescope (NGST) 1000
Expanded Very Large Array (EVAL) 140 Constellation-X Observatory 800
Large-aperture Synoptic Survey Telescope (LSST) 170 Terrestrial Planet Finder (TPF) 200
Single-Aperture Far Infra Red (SAFIR) Observatory 100
Moderate Initiatives
Telescope System Instrumentation Program (TSIP) 50 Gamma-ray Large Area Space Telescope (GLAST) 300
Advanced Solar Telescope(AST) 60 Laser Interferometer Space Antenna (LISA) 250
Square Kilometer Array (SKA) TechnologyDevelopment
22 Solar Dynamics Observatory (SDO) 300
Combined Array for Research in Millimeter-waveAstronomy (CARMA)
11 Energetic X-ray Imaging Survey Telescope (EXIST) 150
Very Energetic Radiation Imaging Telescope ArraySystem (VERITAS)
35Advanced Radio Interferometry between Space andEarth (ARISE)
350
Frequency Agile Solar Radiotelescope (FASR) 26
South Pole Submillimeter-wave Telescope (SPST) 50
3
• Launch in 2005
• 20 MeV to 300 GeV
• Wide-field imaging telescope
• NASA cost is $326 M
• http://glast.gsfc.nasa.gov/
Theme: Exploring Sites of ParticleAcceleration in the Universe
Gamma Ray Large Area Space Telescope
4
Mission Parameters
Energy Range
Energy Resolution (∆E/E)
Effective Area (peak)
Field of View
Angular Resolution
Sensitivity (> 100 MeV)*
Mass
Lifetime
* 2 year survey at high latitudes
EGRET
20 MeV - 30 GeV
0.1
1500 cm2
0.5 sr
5.8° @ 100 MeV0.5° @ 10 GeV
~ 10-7 cm-2 s-1
1810 kg
1991 - 1997
AGILE
30 MeV - 50 GeV
1
700 cm2
~ 3 sr
4.7° @ 100 MeV0.2° @ 10 GeV
5 × 10-8 cm-2 s-1
60 kg
2002 - 2005
GLAST
20 MeV - > 300 GeV
0.1
12000 cm2
2.5 sr
~ 3.5° @ 100 MeV~ 0.1° @ 10 GeV
~ 2 × 10-9 cm-2 s-1
3000 kg
2005 - 2010
5
• Huge FOV (> 20% of sky)
• Broadband (4 decades in energy, including unexploredregion > 10 GeV)
• Unprecedented PSF for gamma rays (factor > 3 betterthan EGRET)
• No expendables Ù long mission without degradation
• Large area (factor > 7 better than EGRET)
• Results in factor > 30 improvement in sensitivity
GLAST Capabilities
6
EGRET All Sky Map (>100 MeV)
CygnusRegion
3C279
Geminga
Vela
Cosmic RayInteractionsWith ISM
LMC
PKS 0528+134
PKS 0208-512
Crab
PSR B1706-44
7
EGRET Discoveries
220 215 210 205 200 195 190 185 180 175 170 165 160Right Ascension
30
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
Dec
linat
ion
220 215 210 205 200 195 190 185 180 175 170 165 160
Right Ascension
30
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
Dec
linat
ion
EGRET: 3C279/3C273
Gamma Ray Blazars
170 Unidentified Sources LMC Detection
75808590
Right Ascension
-74
-72
-70
-68
-66
-64
Dec
linat
ion
9.61e+03
9.61e+03
9.61e+03
2.18e+04
2.18e+04
3.39e+04
4.61e+04
2.18e+04
1.87e-05
2.22e-05
2.58e-05
2.95e-05
3.33e-05
3.69e-05
4.06e-05
4.42e-05
4.79e-05
5.15e-05
5.50e-05Gamma ray image overlayed with 1400 MHz radio contours
Prolonged GeV Emissionfrom GRBs
1.351.35 1.70
10
10
10
10
Time (Hours)
Ph
oto
n E
ner
gie
s (M
eV)
4
3
2
1
8
EGRET Discoveries cont.
5 New Pulsars
Crab
Vela
1706-44
1055-52
Geminga
1951+32
0656 +14
Geminga Radio-Quiet Pulsars
Crab
PKS 0528+134
Geminga
Prolonged GeV Emissionfrom Solar Flares
Time, UT Hours on June 1, 1991
0:00 4:00 8:00 12:00 16:00 20:00 24:00
Ph
oto
ns
(>50
MeV
), cm
-2
s-1
10-5
10-4
10-3
Fla
re: M
5.3
Fla
re: X
12.0
Cosmic Diffuse Background
10-1 100 101 102 103 104 105 106 107 108 109
Photon Energy (keV)
0.1
1.0
10.0
100.0
E2 d
J/dE
(ke
V2 /(
cm2 -s
-keV
-sr)
HEAO A2,A4(LED)
ASCA HEAO-A4 (MED)
APOLLO
COMPTEL
SAS-2
EGRET
ASCA (Gendreau 1995)
HEAO (LED) (Gruber 1992)
HEAO (MED) (Kinzer et al. 1996)
SMM (Watanabe et al.1997)
APOLLO upp. lim (Trombka 1997)
COMPTEL (Kappadath et.al.1996)
SAS-2 (Thompson & Fichtel 1982)
EGRET (Sreekumar et al 1998)
+
9
GLAST versus EGRET: All-Sky Surveys
Virgo Region (E > 1 GeV)
Simulated GLAST One-Year All-Sky Map (E > 100 MeV)
5σ Sources from Simulated One-Year All-Sky Survey
¥ AGN ¥ Galactic Plane¥ 3EG Catalog ¥ Galactic Halo
10
Cygnus Simulation
EGRET Observed GLAST Simulated
11
+90
-90
-180+180
+90
-90
-180+180
= EGRET blazars seen sometimes
= EGRET blazars seen always
= EGRET unidentified high-latitude variables
= Simulated GLAST 20σ AGN detections
+90
-90
-180+180
Gamma-Ray Quasars
• EGRET sees most blazarsonly when they flare
• What is the population ofhigh-energy blazars?
• What is the nature of thequiescent emission?
• What is the relation toradio luminosity andvariability?
• What are the high-latitudeunidentifieds?
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Number and Localization of GLAST AGN
13
Blazar Spectra
• GLAST combined with TeVobservatories will probe thecomplex spectra of blazars
Mrk 501
14
Sources in Third EGRET Catalog
Unidentified Sources
• 172 unidentified sources in3rd EGRET catalog
• Mystery of unidentifiedssince 1970s
• Galactic unidentifieds maybe SNRs, Gemingas,massive stars, molecularclouds, or newphenomenon!
• Mid-latitude sources areseparate population fromlow-latitude sources(Nature, March 23rd issue)
15
• EGRET sourcepositions are ~ 0.5o insize, too large forcounterpart searches
• GLAST will providemuch more accuratesource positions, 30arcsec to 5 arcmin
Solving the Mystery ofUnidentifieds With GLAST
163.0 162.5 162.0 161.5 161.0Right Ascension (J2000)
55.0
55.5
56.0
56.5
57.0
Dec
linat
ion
(J20
00)
163.0 162.5 162.0 161.5 161.0
55.0
55.5
56.0
56.5
57.0
Image from NVSS 1.4 GHz survey, Condon et al. (1998)
EGRET
GLAST
Lockman Hole
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• Supernova shockacceleration modelspredict correct spectraand energetics
• Evidence of TeVelectrons in non-thermalX-ray emission andground-based gamma-ray observations
• Smoking gun would be an extended gamma-ray source, such as aninterstellar cloud, located next to a SNR, which may be the case forGamma Cygni
• This would provide proof that nuclei as well as electrons are acceleratedas predicted
SNR Origin of Cosmic Rays
SNR γ-Cygni
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Gamma Ray Bursts
EGRET:
GLAST:
.278 .556 .833 1.111 1.389 1.6670
10
10
10
10
Time (Hours)
Ph
oto
n E
ner
gie
s (M
eV)
4
3
2
1
GRB 940217
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GLAST Instrument and IDS Selection
• GLAST instruments & InterDisciplinary Scientists (IDS's) selected.
– Large Area Telescope (LAT), PI: P. Michelson, StanfordSi Tracker: Stanford, UCSC, Japan, Italy
CsI Calorimeter: NRL, France
Anticoincidence: GSFCData Acquisition System: Stanford, NRL
– GLAST Burst Monitor (GBM), PI: C. Meegan, MSFCDetectors: MPE
NaI 5 keV - 1 MeVBGO 150 keV - 30 MeV
– IDS'sC. Dermer (NRL) - non-thermal universe
B. Dingus (Wisconsin) - transientsM. Pohl (Ruhr U.) - diffuse galacticS. Thorsett (UCSC) - pulsars
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GLAST LAT
1
2
20
LAT Beam Test Verification
MonteCarlo
Data
21
LAT Hardware
22
GLAST GBM
102
100
10—2
10—4
10—6
10—8
NAI
BGO
LAT
Energy (keV)
Coun
t Rat
e (c
ount
s s—
1 ke
V—1
det—
1 )
101 102 103 104 105 106 107
Low-Energy NaI (TI)Detectors (3 of 12)
High-Energy BGODetector (1 of 2)
GRB 940217
LAT and GBM simulation.
23
GBM vs. BATSE
Parameter
Energy Range
Detectors
FOV
Location Accuracy
Burst Sensitivity
BATSE
25 keV - 1.9 MeV (LAD)
7 keV - 10 MeV (SD)
NaI
Full Sky
2° - 5°
0.2 ph cm-2 s-1
GBM
5 keV - 1 MeV (LED)
150 keV - 30 MeV (HED)
NaI/BGO
8.6 sr
1.5° - 3°
0.6 ph cm-2 s-1
24
AGILE
Optimal orbital parameters
Possible ground station
Spacecraft + payload mass
Payload required power
Downlink telemetry rate
Pointing configuration
Pointing accuracy
Satellite expected life
Spacecraft and Satellite Characteristics
Equatorial orbit, 550 km
Malindi (Kenya)
180-200 kg
~60 W
~500 kbit/sec
3 - axes
0.5 - 1 degree
>~ 3 years
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AGILE and GLAST Performance
26
Space Gamma Ray Astronomy
1998 20102006200420022000 2008
GLAST
AGILE
INTEGRAL
HETE
CGRO
Swift
27
GLAST Long-Term Schedule
Revised12/20/99
Tasks
Date
Project Flow
Project Milestones
NAR
PDR CDR
LAUNCH
Spacecraft
Build I & T
Design Build I &T
Long Lead Procurements
Instr. Selection
MCR
InstrumentTechnology
Build I &T
Instrument Concept Development
Design
SRR
PSR
PER
InstrTech. NRA
Instr.AO
S/C Accom.StudyS/C RFO
S/C Selection
Independent Assessment.
Design
Flight Instrument
MSI &T
Ground System
FY 1998FY 1997 FY 1999 FY 2000 FY 2001 FY 2002 FY 2003 FY 2004 FY 2005 FY 2006
New Start
Launch Vehicle Procurement
Inst. Del.SPR
S/C Accom.Study
S/C Accom.Study
Phase A Phase EPhase C/DPhase BPre Phase A
ImplementationFormulation
Launch Vehicle
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