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?

12

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

16

• 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

17

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

18

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

19

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

25

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