The Fermi Gamma-ray Space Telescope
Hiromitsu Takahashi （高橋弘充）
Hiroshima University （広島大学）
hirotaka@hep01.hepl.hiroshima-u.ac.jp
for the LAT Collaboration
2008 June 11th

Contents• Gamma-ray observation and detectors onboard Fermi• First results• Data archive etc…

Fermi LAT Collaboration
United States
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California State University at Sonoma
University of California at Santa Cruz - Santa Cruz Institute of Particle Physics
Goddard Space Flight Center – Laboratory for High Energy Astrophysics
Naval Research Laboratory
Ohio State University
Stanford University (SLAC and HEPL/Physics)
University of Washington
Washington University, St. Louis
PI: Peter Michelson (Stanford & SLAC)
France•IN2P3, CEA/SaclayItaly•

INFN, ASI

Japanese GLAST Collaboration•••

Hiroshima University
ISAS/JAXA, RIKENTokyo Inst of TechnologySpain•

ICREA and Inst de Ciencies de l’Espi

Swedish GLAST Collaboration•••

Kalmar University
Royal Institute of Technology (KTH)
Stockholm University~270 Members (including ~90 Affiliated
Scientists, plus 37 Postdocs, and 48
Graduate Students)
Cooperation between NASA and DOE, with
key international contributions fromFrance, Italy, Japan and Sweden.
Managed at Stanford Linear Accelerator
Center (SLAC).

GLAST was renamed to Fermi
on Aug 26

Fermi Key Features• Two gamma-ray instruments:

Compared to EGRET:• > 100 MeV, 1 yrsensitivity x25• localization x102
• field of view x5• observing efficiency x2• deadtime x10-3– LAT:
Large Area Telescope• high energy (20 MeV – >300 GeV)(LAT)
– GBM:• low energy (8 keV – 30 MeV)

GLAST Burst Monitor (GBM)• Huge field of view with good angular resolution– LAT: 20% of the sky at any instant; in sky survey mode, expose all parts ofsky for ~30 minutes every 3 hours. GBM: whole unocculted sky at any time.

•Wide energy range, including largely unexplored band
10 GeV - 100 GeV

Fermi Science Targets
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Super-massive black holes (Active Galactic Nuclei)
Gamma-ray bursts (GRBs)
Pulsars, Pulsar wind nebulae (PWNe) Physics of high-energy emission
Galactic binaries
Origin of cosmic-rays
Supernova remnants (SNRs),
Galactic diffuse emission
Solar physics•Optical-UV background light••

High-energy unidentified sources
Dark MatterProbing the era of galaxy formationDiscovery and new sciences

5 yrs EGRET
Detected sources : ~270 (Unidentified : ~170)

1 yr (sim) Fermi

Origin of Cosmic-Rays• Where do protons come ? Cosmic-rays are dominated by protons.
• Photons keep the information of the original source position(complementary to measuring charged particles which are
effected by magnetic field)• We need to detect hadronic interaction, since the emission from
leptonic interaction (synchrotron and inverse-Compton) is mainly from electrons.
RadioX-rayMeVTeV
Molecular cloudAround SNRs, PWNe, …

MeV gamma-rays are very important to reveal accelerated protons directly.

Why Satellites ?
• Only optical and radio emission can reach the ground.
• Then, we need satellites or balloons to observe other wavelengths.

AltitudeTransmittance of the air
Vibration androtation ofmolecules(H2O, CO2, …)

100 km50 km

Photoabsorption byelectrons
Comptonscattering byelectrons

大気分子の振動RadioIROpt.

UV

X-ray

-ray

Interaction of Gamma-Rays• Photoabsorption• Compton scattering• Pair creation (e+, e-)Cross section of Silicon
Photoabsorption

Comptonscattering

Pair creation(e+, e-)MeV-GeV photons are detected through the pair-creation interaction.

Compared to EGRET:• > 100 MeV, 1 yr
sensitivity x25• localization x102
• field of view x5• observing efficiency x2• deadtime x10-3

Large Area Telescope (LAT)• Precision Si-strip Tracker (TKR)-18 XY tracking planes.
- 1 plane consists of single-sided silicon
strip detectors (228 mm pitch) andtungsten converter.
- Measure the photon direction.

Tracker• Hodoscopic CsI Calorimeter(CAL)- Array of 1536 CsI(Tl) crystals in 8 layers.
- Measure the photon energy• Segmented Anticoincidence Detector(ACD)

ACD- 89 plastic scintillator tiles.
- Reject background of charged particles.

e+e–Calorimeter

Systems work together to identify and measure the flux of cosmic
gamma-rays with energy 20 MeV - >300 GeV.

Si-Strip Detector (SSD)
SSD was developed by Hiroshima Univ. and Hamamatsu Photonics in Japan.
High Quality- Fraction of Dead strips: < 0.01%- Very low leakage current; ~2.5 nA cm -29 cm
SSD- Wafer thickness 400 mm- Wafer Area 8.96 x 8.96 cm 2- Strip pitch 228 mm

Total- 11500 SSDs, 1M channels- 93 m2 of Si

Leakage current (nA/cm 2)

Increasing the angular resolution and FOV- SSD (Fermi):~200 mm
Spark chamber (EGRET) :~1 mm

LAT

GBM
Sodium Iodide
Detector
Solar panel

x 12

GBM
BismuthGermanate
Detectorx2

Fermi LAT Performance
http://www-glast.slac.stanford.edu/software/IS/glast_lat_performance.htm•Energy Resolution: ~10% (~5% off-axis)•PSF (68%) at 100 MeV ~ 3.5 deg (thin section)•PSF (68%) at 10 GeV ~ 0.1 deg•Field Of View: 2.4 str

Point Source sensitivity- 1 year all-sky survey- diffuse background flux :1.5x10-5/cm2/s/str (E>100 MeV)
- spectral index : -2.1

Orbit of the Fermi SatelliteSAA

http://observatory.tamu.edu:8080/Trakker/- Launched from Kennedy Space Center on June 11 2008
- Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination- There is no observation during South Atlantic Anomaly (SAA).

Operation Mode

LAT sensitivity on 4
different timescales:
100 s, 1 orbit (96 mins),
1 day and 1 year••In survey mode, the LAT observes the entire sky every two orbits (~3 hours).
The LAT can also perform pointed observations of particularlyinteresting regions of the sky.

•GBM sees entire unocculted sky.

Multiwavelength campaigns with the LAT are always welcome.

Observed Single Gamma-ray Events~ few HzGreen : positions of the charged particles, Blue : reconstructed track trajectories
Yellow : estimated direction of gamma-ray, Red : energy depositions in the calorimeter.

Events are efficiently identified as gamma-rays or charged particles.

First-Light Sky Map with 95 hrs (4 days)
Equivalent to EGRET’s first year!

• Galactic diffuse emission• Pulsars• Blazars
http://www.nasa.gov/mission_pages/GLAST/news/glast_findings_media.html

Vela Pulsar• Well-known bright pulsar• (Pulse-on) – (Pulse-off) : background-free analysis• Good to evaluate the detector response(Timing, PSF, Energy, …)

Period = 89 ms
Movie

http://www.nasa.gov/mission_pages/GLAST/news/glast_findings_media.html

A Radio-Quiet Pulsar in CTA1
Abdo et al. science 2008, October 16
P ~ 317 msPdot ~ 3.6E-13
Characteristic age ~ 10,000 yrs

Location of EGRET source 3EG J0010+7309,
the Fermi-LAT source, and the central X-ray
source RX J0007.0+7303• There is X-ray point source, but the pulsation is only detected with gamma-ray(not X-ray or radio).
• Emission mechanism ? Other EGRET unID sources ?

GCN and ATel Reports• Gamma-ray Burst Coordination Network (GCN)
There are already 3 GRBs detected by the LAT.

• Astronomer’s Telegram (ATel)
Some of bright Blazars and transients in the Galactic plane.

Year 1 Science Operations Timeline Overview

spacecraft
turn-on checkout

week

LAUNCH

week

LAT,GBM
turn-oncheckoutweek“first light”
whole skyStart Year 1
Science Ops
Observatory
renaming

sky survey + ~weekly GRB

pointed + sky
survey tuning

week

Start Year 2
Science Ops

repoints + extraordinary TOOs

month

12 m o n t h s

L+60 days
initial tuning/calibrations

2nd GLAST
Symposium
in-depth instrument studies

Release Flaring and Monitored Source Info

GBM and LAT GRB Alerts

continuous
release of new
photon data

GI Cycle 1
Funds Release
Fellows Year 1
StartGI Cycle 2Proposals
LAT 6-month
high-confidence
source release, GSSC
science tools advance
releaseLAT Year 1 photon
data release PLUS
LAT Year 1 Catalogand Diffuse ModelData Release plan and operations•First Year observations - Sky Survey– After initial on-orbit checkout (60 days), the first year of observations will be asky survey.
– Repoints for bright bursts and burst alerts will be enabled– Extraordinary ToOs will be supported.
– First year data will be used for detailed instrument characterization and key
projects (catalog, background models etc).

•First Year Data release– All GBM data
– Information on all LAT detected GRB (flux, spectra, location)– High level LAT data (time resolved flux/spectra) on ~20 selected sources and on
all sources which flare above 2x10-6, continued until the source flux drops
below 2x10-7 (rate ~ 1-4 such objects per month).
– The LAT team will produce a preliminary source list after ~6 months on a best
effort basis•

Subsequent years: Observing plan driven by guest observer proposal
selections by peer review. Default is sky survey mode.
– All data publicly released within 72 hours through the Science Support Center(GSSC).

•See http://glast.gsfc.nasa.gov/ssc/data/policy/ for more details

LAT First Year Source Monitoring List
• Data are provided for daily
and weekly integrations for allsources.
• A “quicklook” analysis, priority
is to get the results out as
quickly as possible.

• You can download the data fromhttp://heasarc.gsfc.nasa.gov/cgibin//W3Browse/w3table.pl?Action=Detai
led%20Mission&Observatory=fermi

Activities at Hiroshima University• Multiwavelength observations- Optical/Infrared telescope “Kanata”- X-ray satellite “Suzaku”• Monitoring the condition of the LAT detector• Searching transient or Gamma-ray burst events

Conclusions• Fermi was launched on June 11 2008, and all theinstruments were turned on successfully and areworking without any problems.
• Some of data release has been already started.
• More results from the first year data are coming soon.
- Super-massive black holes (Active Galactic Nuclei)- Gamma-ray bursts- Pulsars, Pulsar wind nebulae- Galactic binaries- Supernova remnants- Galactic diffuse emission- Solar physics- Optical-UV background light- High-energy unidentified sources- Dark Matter…
Fermi First-Light Sky Map (95 hrs)