Transcript ppt

How many neutralinos are there?
To determine the current number of neutralinos (relic abundances),
we need to solve the Boltzmann equation for early and late times
Negligible at
earlier times
dn
dt
Hubble
Constant
Negligible at late times
 3Hn    xx v [( n )  (n ) ]
2
Expansion of
universe
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Depletion of
neutralinos
eq 2
Creation of
neutralinos1
Why are we so excited about GLAST?
• GLAST will
– Study gamma radiation from Universe with a
lot more details than previous missions
– explore regions never explored before in space
– gives us insight in how the Universe evolved
• The GLAST Project allows us to
– develop a successful partnership between DOE
and NASA
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Gamma ray Large Area Space Telescope
GLAST will measure the direction, energy and arrival time of g rays
Orbit
575 km,
circular
LAT: main instrument
Inclination
28.5o
Lifetime
5 years (min)
Launch Date
2007
Launch Vehicle
Delta 2920H-10
Launch Site
Kennedy Space
Center
GBM: smaller instrument catching
bursts of radiation
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Why do we need a satellite ?
2007 GLAST
2001 LAT
Balloon Flight
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Why g rays ?
Gamma rays: similar to visible light but with higher frequency
• Universe is transparent to g rays
g
center of galaxies
radiate gamma rays
• g not affected by magnetic fields
• g probes early times of the Universe
satellite
~ 500 km
Gamma rays:
5
most violent energy processes found in Nature
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Light – a Fingerprint of the Universe
Credit; Lund Observatory
Optical
Credit: COBE Team
Infrared
Credit: WMAP
COBE Team
Team
Microwave
Microwave
g Rays
The electromagnetic spectrum carries a lot of information about
the evolution of the Universe
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
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found
300 10,000
objects
in 10inyrs
LAT
:EGRET
expects
to
objects
in 2 yrs
LAT:
expects
to find
find
300 objects
2 days
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Gamma-Ray Bursts
• Last from milliseconds to ~ 100 seconds
• Brightest phenomenon in Universe
• Several bursts expected daily
• Do not know what causes them !
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
AGN - Supermassive Black Holes ?
Black Hole
Extragalactic
Jet
galaxies radiate
gamma rays
(very powerful)
Where does the energy
come from?
Accretion disk
Black holes inside the
galaxy??
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Dark Matter
How is matter measured in the
galaxy?
1. By calculating how fast stars go
around the center of the galaxy
2. By measuring light from the galaxy
and using results in an equation to
obtain amount of matter
1 and 2 give different results !!!!
Strong Evidence that Dark Matter exists
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
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Dark Matter Simulations
Credit: B. Moore, www.nbody.net
Past
z = 20
We do not know what dark
matter is but we can guess
z = 10
z=5
We use simulations to
indicate how dark matter is
formed
z=1
Today
GLAST could measure dark
matter and explain its origins
Simulations of Local Group
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
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GLAST LAT Overview
g
Tracker
ACD
Get rid of
background
Measures
direction
e+
e–
Grid (& Thermal
Radiators)
Calorimeter
Measures
Energy
~150 collaborators
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
How do we see gamma rays?
Eg --> me+c2 + me-c2
LAT detects
the
There
are 100,000
gamma
ray particles
indirectly
charged
through
pairLAT
external
to the
conversions
for every
gamma ray
(into
incharged
space
particles)
Charged
particles
The unwanted
create
current
in each
charged
particle
detector is
background
REJECTED by the
outermost detector
( in green)
Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
g
Charged particle
background
electron
positron
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Two Tower Integration
Installation of
Tower A in Single bay
Tower A in Grid.
Tower B being installed in grid.
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
Overview of LAT Mechanical Systems
Radiator
Cut-outs for possible
S.A. launch locks
Hole to accommodate
Solar Array mast
VCHP reservoirs
LAT in the Delta-II fairing
Radiator Mount Bracket at 4
corners of Grid
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004
GLAST
Feb 2007 launch
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Eduardo do Couto e Silva - ATC/LM Colloquium, June 2004