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Gamma ray Large Area Space Telescope - GLAST

Eγ = 20 MeV - 300 GeV

Explore most powerful sources of acceleration in the universe

GLAST Ambassadors

July 18, 2002

Gary Godfrey - SLAC

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Gamma Rays• Energy = h * frequency (h=4.1 x 10-15 eV-sec)

Radio 10-9 - 10-8 eVTV 10-7 eVInfrared .1 - 1 eVVisable 2 - 5 eVXrays 103 - 105 eVGamma Rays >106 eV

Gamma Rays can’t be reflected by mirrorsWavelength << interatomic distances

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Why do we need a satellite ?

2005 GLAST

2001 GLASTBalloon Flight

~103

g cm

-2

~30

km

Atmosphere:γ

For Eγ < ~ O(100) GeV, must detect above atmosphere (balloons, satellites, rockets)

For Eγ > ~ O(100) GeV, information from showers penetrates to the ground (Cerenkov)

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How are gamma rays generated ?

Accelerated particles interact with matter, magnetic field or photon fields

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16 towers arranged in a 4 x 4 configuration

GLASTGLAST

1 out of 16 towers

LAT

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GLAST Collaboration

a University of California, Santa Cruz, Department of Physics, Santa Cruz, California .b University of Chicago, Department of Physics, Chicago, Illinoisc Commissariat a l’energie atomique (CEA), Saclay, Francee Ecole Polytechnique, Laboratoire de Physique Nucleaire des Hautes Energies

(LPNHE), Palaiseau, France f Hiroshima University, Department of Physics, Hiroshima, Japang The Institute of Physical and Chemical Research, Saitama, Japanh The Institute of Space and Astronautical Science, Sagamihara, Japan i Kanagawa University, Institute of Physics, Kanagawa, Japan j Lockheed-Martin Solar and Astrophysics Laboratory, Lockheed-Martin Advanced

Technology Center, Palo Alto, California k University of Massachusetts at Amherst, Amherst, Massl Max-Planck-Institut für extraterrestrische Physik (MPE), Garching, Germany m NASA Ames Research Center, Mountain View, Californian The NASA/Goddard Space Flight Center, Greenbelt, Marylando The Naval Research Laboratory, Washington, D.C.

p University of Rome, Department of Physics and Instituto Nazionale di Fisica Nucleare, Tor Vergata, Rome, Italy

q Royal Institute of Technology, Stockholm, Swedenr Shibaura Institute of Technology, Department of Electronic Information Systems, Faculty of

Systems Engineering, Shibaura, Japan s Sonoma State University, Department of Physics and Astronomy, Rohnert Park, Californiat Stanford University, Department of Physics; Hansen Experimental Physics Laboratory; Stanford

Linear Accelerator Center, Stanford, Californiau Stockholm University, Stockholm, Sweden v University of Tokyo, Department of Physics, Institute for Cosmic Ray Research, Tokyo, Japan w University of Trieste, Department of Physics, Instituto Nazionale di Fisica Nucleare and Scuola

Internazionale Superiore di Studi Avanzati, Trieste, Italyx University of Turin, Department of Physics, Osservatorio Astronomico, Turin, Italyy University of Washington, Department of Physics, Seattle, Washin gton z University of Wisconsin, Department of Physics, Madison, Wisconsinα Instituto di Fisica Cosmica e Tecnologie Relative, CNR, Milano, Italyβ Boston University, Boston, Massachusettsγ University of Udine, INFN, Italy

>100 Collaborators

>30 Institutions

R. Arnold k

W. Atwood G Barbiellini w

L. Bergstromu

D. Bertsch n

V. Bidoli p

E. Bloomt

J. Bonnelln

P. Bosted kU. Bravar w

T. Burnett y

P. Caraveo αP. Carlson q

A. Celotti w

D. Chenette j

L. Cominsky s

C. Covault b

J. Danzigew

A. de Angelis γ

A. Djannati-Atai e

S. Digel n

B. Dingus z

E. do Couto e Silvat

D. Dorfan a

R. Dubois t

A. Ferrari x

P. Fleury e

T. Francke q

Y. Fukazawa v

N. Gehrelsn

B. Giebels t

M. Gliozzi xG. Godfrey t

I. Grenier c

J. Grove o

H. Gursky o

R. Hartman n

T. Handa t

J. Hernando aM. Hirayama b

S. Hunter n

R. Johnson a

W. Johnson o

T. Kamae t,v

K. Kasahara r

N. Kawai g

T. Kifune v

W. Kroeger a

H. Kubo g

P. Nolan t

J. Norris n

A. Odiant

T. Ohsugi f

R. Ong b

M. Oreglia b

J. Ormes n

J. Paul c

A. Perrino pB. Phlips o

P. Picozza p

P. Ray o

E. Reali p

S. Ritz,n

S. Rock kJ.J. Russell t

H. Sadrozinski a

J. Scargle m

P. Schiavon w

S. Severoni p

G. Share o

J. Skibo o

D. Suson o

Z. Szalata k

T. Takahashi h

T. Tamura i

M. Tavani α

D. Thompson n

S. Torii i

A. Vacchi w

M. Villata x

K. Wood o

A. Yoshida g

K. Yoshida i

P. Kunz t

Y. Lin t

M. Lovellette o

G. Madejski t

J. Mattox βH. Mayer-

Hasselwander l

P. Michelson t

A. Moiseev n

M. Mori v

A. Morselli p

G. Nakano jG. Navarra x

HEAHEP

+ new French and Italian collaborators

Incomplete list

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Si -Pb Tracker

CsI Calorimeter

Large Area Telescope2560 kg, 600 W, 1.73² × 1.06 m

Anti-Coincidence Detector

Delta II

7920 H

Gamma-ray Burst Monitor

International Collaboration

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γ

e+ e- calorimeter (energy measurement)

particle tracking detectors

conversion foils

whenever 3 planes in a row are hit, then read out the event and store its information

Gamma Converts in Tungsten Foil

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• A charge particle interacts with the ACD scintillator and produces light.

• A γ usually goes through the ACD without making any signal.

γ

e+ e- calorimeter (energy measurement)

particle tracking detectors

conversion foils

charged particle anticoincidence shield

ACD (plastic scintillator) for background rejection

ACD Rejects Charged Cosmic Rays

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Strip-shapedPN diode

200 micron wide

400 micron thick high purity silicon

VLSI amplifier

γ

e+e-

Silicon Strip Detector

9 cm

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XGT

ACD

TKRCAL

Pressure Vessel

Support Structure

Balloon Flight Engineering Module

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Charged particle photon

Since there are at least 3 hits in a row, the event is triggered

Problem: In the GLAST orbit there are ~105

times more cosmic rays than photons !

Real data from particle beams produced at SLAC

Beam Test Engineering Module

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• Active Galactic Nuclei (AGN)• Gamma Ray Bursts (GRB)• Diffuse Galactic γ-ray background• Dark Matter (or its absence “MOND”) • Diffuse Extragalactic γ-ray background (relics from the Big Bang)• Pulsars• Cosmic rays•Solar flares

Physics Motivation for GLAST

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Up to 104 times the luminosity of typical galaxy in a volume of one cubic parsec ! (1 pc = 3.1 x 1018 cm ~ 3 light years) (assuming isotropic emission)

Changes in Luminosity in a fraction of a day !

Radiation is emitted at all frequencies !

Active Galactic Nuclei

EGRET

GLAST Energy and timeresolved spectra

Possibility to study flares

Study mechanisms of acceleration and cooling

EGRET

GLAST

γ rays

X rays

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We already know that they occur at cosmological distances, implying energies up to 1054 ergs during burst emission (if we assume isotropic model)

Gamma Ray Bursts

long

short

Time of duration of a burst

16S. G. Djorgovski and S. R. Kulkarni / W. M. Keck Observatory

2 days after burst 2 months after burst

GRB 971214 –12 billion light years away (z =3.42) !(about 5.9 trillion miles for light to travel)

Optical Afterglow

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271 sources169 unidentified

EGRET Sky map

Pointsources

EGRET Gamma Ray Emissions > 100 MeV

Cosmic background…What is the point source contribution ?

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WIMP annihilations could produce such structure.

10-5 ph cm-2 sec-1 sr-1 for Eg > 1 GeV

Search for Dark Matter

Contours of photon intensity after subtraction of “best estimate” of Galactic diffuse model. Data suggests presence of a galactic halo (Dixon et al. 1998).

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Halo WIMP annihilations

Although calculation for γ-rays is less uncertain than for other signals (multi-GeV antiprotons, positrons) a null result will not likely constrain SUSY parameter space.

If SUSY uncovered at accelerators, GLAST may be able to determine its cosmological significance quickly.

If true, there may well beobservable halo annihilations

q

qγγ or Zγ

lines

X

X

Example: X is χ0 from Standard SUSY, annihilations to jets, producingan extra component of multi-GeV γ flux that follows halo density (not isotropic) peaking at ~ 0.1 M χ0

or lines at M χ0. Background is galactic γ ray diffuse.

~

Good particle physics candidate for galactic halo dark matter is the LSP in R-parity conserving SUSY

~~

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Indications for Dark Matter

1) Rotation curves of spiral galaxies go to a constant tangential velocity v at large radii.

v2/r = GMgalaxy/r2 when all galaxy mass is within the radius r. So v should decrease with r, but it doesn’t !! Hence maybe there is invisable Dark Matter.

2) Particle Physicists like looking for Dark Matter. Maybe Dark Matter is SUSY Wimps (neutralinos), or Axions. Theoretically predicted particles that would have been made in the Big Bang.

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MOND“Modified Orbital Newtonian Dynamics” (Sci Am August, 2002)

But is it Dark Matter or Modified Newton ? http://www.astro.umd.edu/~ssm/mond/

Change Newtonian acceleration when the acceleration is very small:

Acceleration = GM/r2 -> sqrt( GM/r2 * a0) when Acceleration < a0

v2/r = sqrt( GMgalaxy/r2 * a0 v4 = GMgalaxy * a0

1) Galaxys’ tangential velocity is now a constant at large radii.

2) If we assume Mgalaxy/Lummeasured ~ 2, then a0~ 2 x 10-8 cm/sec2 seems to be the same number for all spiral galaxies looked at !

3) An experimental regularity called “Tully Fisher” V4 α Lum is explained.

4) The Hubble Constant = 7 x 10-8 cm/sec2 (is ~a0 just a coincidence?)

GLAST will set limits (or see the it!) on how much of certain forms of Dark Matter can be trapped in our Galaxy. If no Dark Matter, maybe MOND ?

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http://octopus.gma.org/surfing/satellites/about.html

Low Earth Orbit (LEO) 200-500 miles (320–800 km)

Which orbit ?

Geostationary Orbit (GEO)

~22000 miles (~35000 km)

(must travel fast)

(higher background)

Communicationsatellite

GLAST

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flux is 20-30 times higher (low energy)

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•1997 Test Beam validation of measurement principles and technology choices. W.B. Atwood et al SLAC-PUB-8166 (1999), NIM A 446, (2000), 444.

•1999/2000 Test Beamfull engineering model including compact front end electronicsE. do Couto e Silva et al SLAC-PUB-8682 (2000), accepted for publication in NIM A

•2001 Balloon FlightNext step in full flight software development and improvements based upon 1999/2000 test beam experience

•2003/2004 Calibration Beam testsFull calibration of instrument and response matrices

•2006 March, Launch

GLAST timeline

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271 sources including 169 unidentified sources 5 Gamma Ray Bursts6 pulsars

~70 AGN

EGRET (1991) 20 MeV - 30 GeV

Spark Chamber

~25 sources 1 extragalactic source (3C273)

COS-B (1975) 50 MeV – 5 GeV

Spark Chamber

Galactic diffuse emission~10 Galactic sources

SAS-2 (1972) 30 MeV - 0.2 GeV

Spark Chamber

Hint of Galactic diffuse emission

OSO-III (1967) 50 MeV - 0.5 GeV

Proportional Counter

Gamma Ray Astronomy in Space

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EGRET

GLAST

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EGRET

20 MeV - 30 GeV

1500 cm²

0.5 sr

~ 10-7 γ cm-2 s-1

15 ’

100 ms

LAT (min) Improvement

20 MeV - 300 GeV

> 8000 cm² > 6

> 2.0 sr > 4

< 6 10-9 γ cm-2 s-1 > 20

< 0.5 ’ > 30

< 100 µs > 100

Energy

Surface

Field of view

Sensitivity (1yr)

Localization

Deadtime

From EGRET to LAT…

•Large area•Low instrumental background

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GLAST Performance

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EGRET 95%l¡

5σ LAT source r = 7 ’5σ LAT source r = 7 ’

0.5°

Rosat or Einstein X-ray source

! 1.4 GHz VLA radiosource

LAT 95%3EG1911-2000r = 0.3 ’

Identification of Sources

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LAT Science capabilities - sensitivity

200 γ bursts per year prompt emission sampled to > 20 µs

AGN flares > 2 mntime profile +∆E/E ⇒ physics of jets and acceleration

γ bursts delayed emission

all 3EG sources + 80 new in 2 days⇒ periodicity searches (pulsars & X-ray binaries)

⇒ pulsar beam & emission vs. luminosity, age, B

104 sources in 1-yr survey⇒ AGN: logN-logS, duty cycle,

emission vs. type, redshift, aspect angle⇒ extragalactic background light (γ + IR-opt)⇒ new γ sources (µQSO, external galaxies, clusters)

1 yr

100 s

1 orbit

1 day3EG limit

0.01

0.001LAT 1 yr2.3 10-9

cm-2s-1

large field-of-view

Scan mode during 1st year