Gamma-ray Large Area Space Telescope

1. Gamma-ray Large Area Space Telescope High Energy Gamma Physics with GLAST Monica Pepe INFN Perugia on behalf of the GLAST-LAT Collaboration 32nd International Conference on High Energy PhysicsAugust 16-22, 2004, Beijing, China

2. GLAST : Motivations and Goals Study of theorigin of the Universeand itsevolution: strong connection between Astrophysics and HEP with many areas of collaboration GLAST is a partnership of HEP and Astrophysicscommunities sharing scientific objectives and technology expertise: • Designed to use very performant particle detectors order of magnitude inprovement in sensitivity and resolution wrt previous missions • Sky survey in the 10 keV – 300 GeV energy range( poorly observed region of the electromagnetic spectrum ) Use of high resolution and reliable particle detectors is now possible in space after long and successful experience in particle physics

3. Spacecraft The GLAST Mission High Energy Gamma Ray observatory: 2 instruments GLAST Burst Monitor (GBM) 10 keV - 25 MeV (correlative transient observations) Large Area Telescope (LAT) 20 MeV - >300 GeV • Observe, with unprecedented detail, sites of particle acceleration in the Universe • Explore nature highest energy processes (10 keV – >300 GeV) • Answer to important outstanding questions in high energy astrophysics raised by results from EGRET

4. 0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV Active Galactic Nuclei Unidentified sources Cosmic ray acceleration Solar flares Pulsars Dark matter (A. Morselli talk) Gamma Ray Bursts GLAST science capabilities

5. AGILE Covering the Gamma-Ray Spectrum • Broad spectral coverageis crucial for studying and understanding most astrophysical sources • GLAST and ground-based experiments cover complementary energy ranges • Performance: wide FOV and alert capabilities for GLAST/ large effective area and energy reach for ground-based • Overlap: between GLAST and Cherenkov allows energy and sensitivity calibrations for ground-based instruments in the 50-500 GeV energy range Predicted sensitivities to a point source: EGRET, GLAST, ARGO, AGILE, Milagro: 1yr survey Cherenkov telescopes:50 hours on source GLAST goes a long way toward filling in the energy gap between space-based and ground-based detectors. There will be overlap for the brightest sources.

6. Sky Map GLAST Survey: ~10000 sources in 2 years 3rd EGRET Catalog (1991-2000) (~ 300 sources)

7. Identifying Sources GLAST 95% C.L. radius on a 5 source, compared to a similar EGRET observation of 3EG 1911-2000 Unidentified Sources 170/271 3rd EGRET Catalog sources still unidentified Counting stats not included. GLAST high angular resolution and sensitivity: • provide source localization at the level of arc-minute • determine Energy spectra over a broad range and Time variability on many scales correlate -ray detections with sources in other wavebands and discriminate between source models Cygnus region (150 x 150), E > 1 GeV

8. Active Galactic Nuclei EGRET discovery: AGN are bright and variable sources of high energy -rays • AGN signature • vast amounts of luminosity (1049erg/s) and energy (spectra extending to GeV and TeV regions) from a very compact central volume • high variability on a time scale <1 day • highly-collimated relativistic particle jets Hypotesis: relativistic plasma ejected from accreting super-massive black holes (106 - 1010 solar masses)

9. AGN Physics with GLAST • Increase the number of known AGN from ~80 to ~5000 • Distinguish leptonic (SSC/ECS) and hadronic (pp / p) models of jets by detailed spectra studies of emitted gammas • Multiwavelenght analysis combining timing and spectral information to determine acceleration and emission sites in the jet Integral Flux (E>100 MeV) cm-2s-1 • Study the redshift dependence of cutoff in the -ray spectra at large z to probe interaction with extragalactic background light (EBL) • Determination of EBL may help to distinguish models of galaxy formation

10. GBM LAT Gamma-Ray Bursts • most distant and intense sources of high energy -rays • cosmological distances (afterglow redshift up to z=5) • isotropic distribution in the sky • transient signal ~ 100 s time scale • EGRET:few statistics @ E>50 MeV, no temporal studies • at high energies (large dead time) GLAST: > spectral studies over full range to discriminate emission models (Synchroton, ICS) > Detection of  rays during brief intense pulses (~10 sdead time) • LATsuited to study the GeV tail of the GRB spectrum • GBMwill cover the range 10 keV-25 MeV and will provide a hard X-ray trigger for GRB GLAST will detect 200 GRB’s/yr with E >100 MeV

11. Pulsar Physics with GLAST known gamma-ray pulsars • LAT high time resolution and • detection efficiency • Direct pulsation search in the -ray • band in all EGRET unidentifyed sources • Detect ~250 new gamma-ray pulsars VELA Pulsar LAT large effective area • High photon statistics, detailed spectra • Discriminate between polar cap • and outer gap emission models of • -ray production -ray beams broader than their radio beamsmany radio quiet pulsars to be discovered

12.  Tracker e– e+ ACD [surrounds 4x4 array of TKR towers] Calorimeter Overview of LAT • Precision Si-strip Tracker (TKR) • - 18 XY tracking planes • - Single-sided silicon strip detectors • - (228 m pitch), 8.8 ·105 channels • - Measure photon direction – Gamma ID • Hodoscopic CsI Calorimeter (CAL) • - Array of 1536 CsI(TI) crystals in 8 layers • - 6.1 ·105channels • - Measure photon energy. Image the shower • Anticoincidence Detector (ACD) • - 89 plastic scintillator tiles surrounding towers • - Reject background of charged cosmic rays • - Segmentation removes self-veto effects • at high energy • Electronics and Flying Software DAQ • Includes flexible and robust • Hardware trigger and Software filters 4x4 modular array 3000 kg – 650 W Electronics and DAQ Systems work together to identify and measure the flux of cosmic gamma rays with energy 20 MeV - >300 GeV

13. Pair-Conversion Telescope One Tracker Tower Module  Anticoincidence shield conversion foil particle tracking detectors e– e+ Carbon thermal panel Electronics flex cables GLAST Tracker Design Overview calorimeter • 16 “tower” modules, 37cm  37cm of active cross section • 83m2 of Si, 11500 SSD, ~ 1M channels • 18 x,y planes per tower, 19 “tray” structures: - 12 with 3% X0 on top (“Front”) - 4 with 18% X0 on bottom (“Back”) – SuperGlast - 3 with no converter Every other tray is rotated by 90°, so each converter foil is immediately followed by an x,y plane of detectors • Electronics on sides of trays: Minimize gap between towers 9 readout modules on each of 4 sides GLAST LAT Tracker is the largest Si-tracker ever built for space applications

14. May 2007 • Science operation begins! GLAST Master Schedule • August 2004 • Assembling of first tower completed • July 2005 • Completion of the LAT – Environmental testing • December 2005 • Delivery to Observatory Integration – • Mate with Spacecraft and GBM and test • February 2007 • Kennedy Space Flight Center LAUNCH Gravity Probe B Launch on Delta II