Extreme Astrophysics
icecube.wisc.edu/~halzen
• the sky @ > 10 GeV photon energy
< 10-14 cm wavelength
• > 108 TeV particles exist
• they should not
• more/better data
arrays of air Cherenkov telescopes
104 km2 air shower arrays
km3 neutrino detectors
CMB
Radio
Visibe
GeV g-rays
Flux
Energy (eV)
1 TeV
Particle propagation in the Universe
protons E>1019 eV (30 MLy)
neutrinos
gammas (0.01 - 3 MLy)
protons E<1019 eV
Photons:
Protons/nuclei:
Cosmic
accelerator
absorbed on dust and radiation;
deviated by magnetic fields, reactions with radiation (CMB)
With 103 TeV energy, photons do not
reach us from the edge of our galaxy
because of their small mean free path
in the microwave background.
g + gCMB
+
e
+
e
Interaction length of protons
in microwave background
p + gCMB
p+n
lgp = ( nCMB p+g
s CMB ) -1
@ 10 Mpc
GZK cutoff energy > 5 107 TeV
/
/
/
/
/
/
/ TeV sources!
/
/
cosmic
/
rays
/
/
/
/
/
/
/
n
GeV g-rays
Visible
CMB
Radio
Flux
Energy (eV)
Multi-Messenger Astronomy
protons, g-rays, neutrinos, gravitational waves as
probes of the high-energy Universe
1.
protons: directions scrambled by magnetic fields
2.
g-rays : straight-line propagation but
reprocessed in the sources, extragalactic
backgrounds absorb Eg > TeV
3.
neutrinos: straight-line propagation,
unabsorbed, but difficult to detect
Telescope
User
date
Intended Use
Actual use
Optical
Galileo
1608
Navigation
Moons of Jupiter
Optical
Hubble
1929
Nebulae
Expanding
Universe
Radio
Jansky
1932
Noise
Radio galaxies
Micro-wave
Penzias,
Wilson
1965
Radio-galaxies, noise
X-ray
Giacconi …
1965
Sun, moon
Radio
Hewish,
Bell
1967
Ionosphere
Pulsars
g-rays
military
1960?
Thermonuclear
explosions
Gamma ray
bursts
3K cosmic
background
neutron stars
accreting binaries
New Window on Universe?
Expect Surprises
the accelerators
cosmic rays
T. Gaisser 2005
~E-2.7
Nature
accelerates
particles 10 7
times the energy
of LHC!
knee
1 part m -2 yr-1
Ankle
1 part km-2 yr-1
where?
how?
LHC
~E-3
~E-2.7
Galactic and Extragalactic Cosmic Rays
Knee
Ankle
extragalactic
cosmic rays
the highest
energies
Acceleration to 1021 eV ?
2
~10
Joules
~ 0.01 MGUT
dense regions with exceptional
gravitational force creating relativistic
flows of charged particles, e.g.
• dense cores of exploding stars
• supermassive black holes
• merging galaxies
solar flare shock acceleration
Coronal mass
ejection
09 Mar 2000
Cas A Supernova Remnant in X-rays
Shock fronts
Fermi acceleration
John Hughes, Rutgers, NASA
Active Galaxy
Radiation Field:
Ask Astronomers
• energy in protons ~
energy in electrons
• photon target observed
in lines
>> few events per year km2
Active Galactic Nucleus
(Artist Impression)
Jets
Shock fronts
Fermi acceleration
Black Hole
Accretion Disk
Gamma Ray Bursts
Fireball: Rapidly expanding collimated jet of photons, electrons
and positrons becoming optically thin during expansion
Shocks: external collisions with interstellar material (e.g. remnant—
guaranteed TeV neutrinos!!!) or internal collisions when slower
material is overtaken by faster in the fireball.
Protons and photons coexist in the fireball
sources of the highest energy cosmic rays ?
Cosmic Accelerators
E ~ G qvBR
R~
2
GM/c
energy
magnetic
field
E ~ G qBM
boost
factor
mass
pulsar
E (eV) = B (Tesla)
2
R
(m)
2p
__
T
R
B
T-1
ms-pulsar
10 km
108 T
103
Fermilab
few km
few T
105 (#revs-1)
E
1019 eV
~1012 eV
= 1 TeV !
E~GBM
E > 1019 eV ?
• quasars
G @ 1 B @ 103G M @ 109 Msun
• blasars
G >~ 10
• neutron stars G @ 1 B @ 1012G M @ Msun
black holes
..
• grb
G >~ 102
emit highest energy g’s!
models of cosmic rays
Bottom up
– GRB fireballs
– Jets in active galaxies
– Accretion shocks in
galaxy clusters
– Galaxy mergers
– Young supernova
remnants
– Pulsars, Magnetars
– Mini-quasars
–…
• Observed showers either
protons (or nuclei)
Top-down
– Radiation from
topological defects
– Decays of massive
relic particles in
Galactic halo
• mostly pions (neutrinos,
photons, not protons)
Disfavored!
• Highest energy cosmic rays
are not gamma rays
• Overproduce TeV-neutrinos
1024 eV = 1015 GeV ~_ MGUT
are cosmic rays the decay product of
• topological defects ?
(vibrating string, annihilating monopoles)
•heavy relics ?
Top. Def.
X,Y
W,Z
quark + leptons
• top-down spectrum
• hierarchy n >> g >> p
Georges Lemaitre
believed that cosmic
rays where primordial
radiation from the Big
Bang
detection of cosmic rays
Cosmic Rays Observations
first discovered in
1912 by Austrian
scientist Victor
Hess, measuring
radiation levels
aboard a balloon at
up to 17,500 feet
(without oxygen!)
the Earth’s atmosphere as the detector
Cherenkov
radiation
cherenkov radiation: particle’s speed exceeds the speed of light
Copyright © 2001 Purdue University
Use the Phenomenon of Cherenkov light
How to Build a n Detector
1019 eV proton
6 km
p
g
e
m
p0
p+
p-
12 km
g g nm m+ n me+ e-
e+ g
e+
em+
g
e+
n
ne m
electrons/positrons
muons
photons
neutrons
Akeno giant air
Shower array
AGASA
~ 100 km2
Typical HiRes
Stereo Events
HiRes 2
HiRes 1
Mirror and Camera
HiRes in Utah Desert
mirror
Typical HiRes
Stereo Events
• HiRes 2
• HiRes 1
Two Spectra:
HiRes Mono and Fly’s Eye Stereo
HiRes-1: 6/97-2/03
HiRes-2: 12/99-9/01
• Excellent
agreement
between HiRes I
and II.
•
HiRes Stereo
soon!
AGASA @#>?& !
Auger
combine two succesful
techniques
•
fluorescence eye with
active photodetectors
(HiRes)
•
ground array of particle detectors
(AGASA)
Galactic and Extragalactic Cosmic Rays
Knee
1 event
km-2 yr-1
Ankle
extragalactic
cosmic rays
the highest
energies
Auger:
on its way
towards
resolving the
discrepancy
proton
astronomy ?
Pointing:
dB
d
___
____
~
 =
=
E
Rgyro

___
~
0.1o =
[
d
______
1 Mpc
][
B
______
10-9 G
]
E
_________
3 x 1020 eV
B ~ 10-6 Gauss in local cluster?