The VHE gamma-ray sky
viewed with H.E.S.S.
Werner Hofmann
MPI für Kernphysik
Heidelberg
HESS = High Energy Stereoscopic System
© Philippe Plailly
H.E.S.S
Imaging g - induced air showers
Threshold ~ 100 GeV
Sensitivity ~ 1% Crab in 25 h
© Philippe Plailly
Gammaray
Particle
shower
~ 10 km
Detection of
TeV gamma
rays
using Cherenkov
telescopes
~ 1o
Key issue:
huge detection area
~ 105 m2
~ 120 m
Air showers
look a bit like meteors
M
(from Sky & Telescope)
Thermal Emission
5 decades in frequency missing!
 Origin of Cosmic Rays ?
 Cosmic particle accelerators imaged
using (secondary) gamma rays
p + nucleus  p +X
po  gg
p±  m± n
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Supernova remnant shells
alias Vela Junior
RXJ 1713.7-3946
Particle acceleration to beyond 100 TeV
E-2
Index ~ 2.0
Cutoff or break at ~20 TeV
Index constant across SNR
How could cosmic accelerators work?
No. of particles
Man-made accelerators
Energy
How could cosmic accelerators work?
Nature’s accelerators
No. of particles
Enrico
Fermi
Energy
No. of particles
Man-made accelerators
Energy
How could cosmic accelerators work?
Nature’s accelerators
Energy gain / cycle DE/E ~ bshock
... many 100 cycles to reach TeV energies …
... takes several 100 years
Generates power law spectrum dN/dE ~ E-(2+e)
… at some point, particle falls behind shock …
Peak energy ~1015 eV
… depending on size of shock front …
typical Ep  10 Eg
… accelerated particles generate plasma waves …
No. of particles
Nonlinear process with efficiency ~50%!
Energy
Puzzling: X-ray – g-ray correlation
H.E.S.S.
HESS
gamma rays
Suzaku
X-rays
Contour lines: ASCA X-rays
Y. Uchiyama et al. 2002
Suzaku:
Y. Uchiyama, T. Takahashi
Texas Symp. 2006
The Vela region
Vela (Rosat)
Vela Junior
d ≈200 pc
age ≈ 700 y
Gamma ray sources & their physics
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Cosmology with gamma rays
Gamma ray sources & their physics
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Cosmology with gamma rays
Supernova shell
PWN
G21.5-0.9 in X-rays
Chandra / H.Matheson & S.Safi-Harb
Vela-X
Chandra
ROSAT
contours
Peak energy output
at ~10 TeV
Pulsar
wind
nebulae
g-ray sources
are
extended
O(10 pc)
displaced
from pulsar
Morphology of gamma-ray sources:
HESS J1825-137
> 2.5 TeV
1 – 1.5
2.5 TeV
< 1 TeV
Gamma ray sources & their physics
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Cosmology with gamma
rays
Gamma ray sources & their physics
Microquasar
Gamma-ray
period:
3.908±0.002 days
LS 5039
• 4 (?) M object in eccentric
3.906-day orbit around 20-30
M star
• closest approach ~1012 cm or
~2 stellar radii
Spectral variation
unique chance to
“experiment” with
a cosmic source by
varying conditions
Modulation due to
absorption by gg  e+e-
Gamma ray sources & their physics
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Cosmology with gamma rays
“Dark” sources: Objects
which only shine in gamma rays !
… without plausible counterparts in X-rays, radio, …
Not all remain dark: HESS J1813-178
promoted from unidentified source to SNR / PWN
S. Funk et al., astro-ph/0611646
XMM
Radio
HESS J1813-178
Supernova shell
D.J. Helfand et al.,
White et al. 2005
astro-ph/0505392
C.L.
Broganetetal.
al., 2005
Brogan
astro-ph/0505145
20 cm VLA
Ubertini et al., 2005
Integral
TeV
size
Explanations …
Old supernova remnants
(Yamazaki et al., astroph/0601704)
Old PWN
GBR remnants (Atoyan et al.,
astro-ph/0601704)
Basic idea: electrons are gone sensitivity
inHESS
old objects
Stellar winds / OB assoc.
DM halo objects
A tour of galactic
particle accelerators:
Supernova remnants
Pulsar wind nebulae
Binaries
“Dark sources”
Galactic center & DM (?)
Cosmology with gamma rays
Rainer Schödel
The center of our Galaxy
H.E.S.S.
Galactic plane
HESS error circle
Sgr A*
Sgr A East
SNR (radio)
The center of our Galaxy
H.E.S.S.
Galactic plane
The center of our Galaxy
H.E.S.S.
p
Galactic plane
“Diffuse” g-rays tracing
molecular clouds
Point sources subtracted
g
Origin of
Top-down: Annihilation
dark
matter rays
theofGC
gamma
particles
   qq, gg
Generates
characteristic density
profile:
sharp spike
with long tail
and characteristic
energy spectrum
~ quark fragmentation
+ some t decays
?
Is it DM?  Angular distribution
NFW Dark Matter
H.E.S.S. PSF
PRL, in press
Is it DM?  Angular distribution
Diffuse
emission
subtracted
H.E.S.S. PSF
PRL, in press
Is it DM?  Spectrum
-11
10
E2F(E) [TeV/cm2s]
Preliminary
proposed after
early H.E.S.S.
data
10-12
20 TeV Neutralino
20 TeV KK particle
10-13
0,1
1
E [TeV]
proposed before
H.E.S.S. data
10
Extragalactic TeV astronomy
Physics of AGN jets
Cosmology: Density of cosmological
extragalactic background light (EBL)
Quantum gravity & exotics
PKS 2155-304
MJD 53944
15 x Crab flux
1 minute bins
Variability time scale ~ 3 min
Rs/c ~ 150…300 min (1…2 x 109 M)
Fast variability
g
… and quantum gravity
© Lynette
Cook