1ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Gamma-ray Large Area Gamma-ray Large Area Space TelescopeSpace Telescope
High Energy Gamma Physics
with GLAST
Monica Pepe
INFN Perugia
on behalf of the GLAST-LAT Collaboration
32nd International Conference on High Energy
Physics August 16-22, 2004, Beijing, China
2ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Use of high resolution and reliable particle detectors is now possible
in space after long and successful experience in particle physics
Study of the origin of the Universe and its evolution : strong connection between Astrophysics and HEP with many areas of collaboration
GLAST : Motivations and GoalsGLAST : Motivations and Goals
GLAST is a partnership of HEP and Astrophysics communities 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 )
3ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
The GLAST Mission
Spacecraft
GLAST Burst Monitor (GBM) 10 keV - 25 MeV(correlative transient observations)
Large Area Telescope (LAT) 20 MeV - >300 GeV
High Energy Gamma Ray observatory: 2 instruments
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
4ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
GLAST science capabilitiesGLAST science capabilities
0.01 0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeVGeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV
Cosmic ray acceleration
Active Galactic NucleiUnidentified
sources
Pulsars
Gamma Ray Bursts Dark matter (A. Morselli talk)
Solar flares
5ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Predicted sensitivities to a point source:
EGRET, GLAST, ARGO, AGILE, Milagro: 1yr survey Cherenkov telescopes: 50 hours on source
Covering the Gamma-Ray Spectrum Broad spectral coverage is 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 rangeGLAST 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.
AGILE
6ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
GLAST Survey: ~10000 sources in 2
years
3rd EGRET Catalog (1991-2000)
(~ 300 sources)
Sky Map
7ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Counting stats not included.
Cygnus region (150 x 150), E > 1 GeV
GLAST 95% C.L. radius on a 5 source, compared to a similar EGRET observation of 3EG 1911-2000
170/271 3rd EGRET Catalog sources still unidentified
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
Identifying Sources
GLAST high angular resolution and sensitivity:
8ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
AGN signature
• vast amounts of luminosity (1049 erg/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
Active Galactic Nuclei
EGRET discovery:
AGN are bright and variable sources of high energy -rays
Hypotesis: relativistic plasma ejected from accreting super-massive black holes (106 - 1010 solar masses)
9ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
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
• 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
Integral Flux (E>100 MeV) cm-2s-1
10ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
• 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)
Gamma-Ray Bursts
• LAT suited to study the GeV tail of the GRB spectrum
• GBM will cover the range 10 keV-25 MeV and will provide a hard X-ray trigger for GRB
GBM
LAT
GLAST: > spectral studies over full range to discriminate emission models (Synchroton, ICS) > Detection of rays during brief
intense pulses (~10 s dead time)
GLAST will detect 200 GRB’s/yr with E >100 MeV
11ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
known gamma-ray pulsars
LAT large effective area
High photon statistics, detailed
spectra
Discriminate between polar cap
and outer gap emission models of -ray production
-ray beams broaderthan their radio beams many radio quiet pulsars to be discovered
Pulsar Physics with GLAST
VELA Pulsar
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
12ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Systems work together to identify and measure the flux of cosmic gamma rays with energy 20 MeV - >300 GeV
e+ e–
Calorimeter
Tracker
ACD [surrounds 4x4 array of TKR towers]
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 ·105 channels- 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 DAQIncludes flexible and robust Hardware trigger and Software filters
4x4 modular array
3000 kg – 650 WElectronics and DAQ
13ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
• 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 converterEvery other tray is rotated by 90°, so each converter foilis 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
Electronics flex cables
Carbon thermal
panel
One Tracker Tower Module
e+ e–
particle tracking detectors
conversion foil
Anticoincidence shield
Pair-Conversion Telescope
calorimeter
GLAST Tracker Design Overview
GLAST LAT Tracker is the largest Si-tracker ever built for space applications
14ICHEP 04 - August 16-22, 2004, Beijing Monica Pepe – INFN Perugia
Gravity Probe B Launch on Delta II
• 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 2007Kennedy Space Flight Center
LAUNCH
GLAST Master Schedule
•May 2007
Science operation begins!