Transcript Very High Energy Gamma Ray Astronomy Paula Chadwick, Dept. of Physics

Very High Energy Gamma
Ray Astronomy
Paula Chadwick, Dept. of Physics
University of Durham
The Plan
•
•
•
•
The basics
The international context
Some recent results
The future
1011 – 1012 eV
Satellite-based:
511 keV to around
50 GeV
Ground-based:
~20 GeV+
The first VHE Gamma Ray
Telescope
Imaging
Atmospheric
Cherenkov
Technique
•
•
•
•
•
(Multiple) Images of showers
Gamma rays form consistent
pattern
Excellent gamma-hadron
separation (~100%)
Showers located to ~0.1° at
threshold
Point source location to ~ 20”
Important features of the technique…..
Excellent source
location
Very large effective area
Cannot observe
during full moon
IACTs are pointing
instruments
Clouds are bad!
Energy threshold (and
collection area) increase
with zenith angle.
MAGIC
Single 17m diameter telescope
(MAGIC II on its way)
Camera 396 1” PMTs plus 180 1.5” –
high QE
Carbon fibre structure
In operation since November 2003
Roque de los Muchachos, 2 km a.s.l
Institut de Física d'Altes Energies, Barcelona
Universitat Autònoma de Barcelona
Institut für Physik, Humboldt-Universität Berlin
Crimean Astrophysical Observatory
University of California, Davis, USA
Division of Experimental Physics, University of Lodz
Universidad Complutense, Madrid
Max-Planck-Institut für Physik, München
Dipartimento di Fisica, Università di Padova and INFN sez. di Padova, Italy
Detektorphysik und Elektronik, Fachbereich Physik, Universität-GH Siegen
Dipartimento di Fisica, Università di Siena and INFN sez. di Pisa, Italy
Institute for Nuclear Research and Nuclear Energy, Sofia
Tuorla Observatory, Pikkiö, Finland
Dipartimento di Fisica dell'Università di Udine and INFN sez. di Trieste, Italy
Universität Würzburg
Yerevan Physics Institute, Cosmic Ray Division, Yerevan
Institute for Particle Physics, Swiss Federal Institute of Technology (ETH) Zurich
VERITAS-4
Four 12m diameter telescopes
Davies-Cotton design, 345 mirrors
FoV 3.5°
499 PMTs, pixel spacing 0.15°
Two telescopes operating in stereo
mode
Four telescope array now operating
Integrated Pulse
USA: Smithsonian Astrophysical
Observatory; Iowa State
University;University of California, Los
Angeles; University of Chicago;
University of Utah; Washington
University, Saint Louis
UK: Leeds University
Canada: McGill University
Ireland: National University of Ireland
CANGAROO III
Four 10m telescopes
Parabolic design, 114 mirrors each 80 cm diameter
FoV 4°
T1 has 552 pixel camera (0.5”, 0.115°), others 427
pixel (0.75”, 0.168°)
Full array operational since March 2004
Two telescopes struck by lightning Summer 2004 –
now running as 3 telescopes only
136.786 degree E, 31.099 degree S, 160m a.s.l.
High Energy Stereoscopic System
– H.E.S.S.
Four 13m diameter telescopes
Davies-Cotton design, 382 0.6 m diameter
mirrors
FoV 5°
960-pixel cameras
Routine operations since January 2004
23°16'18'' S, 16°30'00'' E 1.8 km a.s.l
M-PIK Heidelberg; Humboldt University, Berlin; University of
Hamburg; Ruhr University, Bochum; Landessternwarte
Heidelberg
LLR Ecole Polytechnique, LPNHE, PCC College de France,
University of Grenoble, CERS Toulouse, CEA Saclay,
Observatoire de Paris-Meudon, University of Montpellier II
Durham University
Leeds University
Dublin Institute for Advanced Studies
Charles University, Prague
Yerevan Physics Institute, Armenia
University of Namibia
North-Western University, South Africa
Nicolaus Copernicus Astronomical Centre, Warsaw
Astronomical Observatory, Jagiellonian University, Cracow
Science with VHE Gamma Rays
Dunkle
Materie
Origin of
cosmic rays
SNRs
Pulsars
and PWN
Space-time
& relativity Dark matter
AGNs
GRBs
Cosmology
Progress in VHE Gamma Rays…
Source Type
Pulsar wind nebula (Crab, MSH15-52…)
SNRs (Cas A, RXJ1713….)
Binary Pulsar (PSR B1259-63)
Binary Systems (LS5039, LSI +61º303)
Diffuse (Cygnus region, Gal. Plane)
AGN (PKS2155-304, Mkn 421…)
Unidentified
TOTAL
2003
1
2
0
0
0
7
2
12
Plus 1 star cluster & the galactic centre………
2005
X
6 14
X9
6
1
1X 5 (?)
1
X2
11
X 14
6
X 10
X 55
32
57
Improvement in Sensitivity –
The Crab Nebula
The Crab Nebula is the
‘standard candle’ in this field –
it is a bright, constant source
of gamma rays right up to
several 10s of TeV.
Crab flux
fraction
Obs. Time
required
0.005
100 hr
0.01
25 hr
0.05
1 hr
0.1
20 min
0.5
1.5 min
1
30 sec
G0.9+0.1
A well-known composite SNR
Compact (2’) core identified as a pulsar wind nebula
Extended (8’) shell
XMM-EPIC images, with 1.5 GHz radio
contours superimposed: Porquet et al.,
A&A, 401, 197 (2003)
G0.9+0.1 – H.E.S.S. Results
Total significance ~13 after 50h
Flux is ~2% of Crab at E > 200 GeV
Not an EGRET source
Spectrum seems to fit well with PWN
origin
The Wings of the Kookaburra
Radio 20 cm (ACTA)
Roberts et al. 1999
The Wings of the Kookaburra
HESS J1420-607
HESS J1418-609
Preliminary
Pulsations from Pulsars?
No!
No!
No!
Vela region
Vela (Rosat)
Vela Junior
d ≈200 pc
age ≈ 700 y
The cosmic ray spectrum…..
‘Messengers from the
extreme universe’
An (almost) featureless
spectrum, so hard to
interpret.
An isotropic flux, mostly
protons
How do we create it?
Cosmic Rays from SNRs
•
•
•
•
One supernova produces around 1046J
Assume one SN every 100 years
Provides a total power of around 3 x 1036 W
Each SN needs to put around 10% of its
energy into high energy particles
• Shock acceleration can naturally explain the
power law spectrum
• Heavy particles are also produced naturally
Imaging cosmic accelerators
 Image accelerators with neutral secondaries
 Gamma-ray and Neutrino Astronomy
particle
physics 
g rate
= cross section
x beam
?
x target
p + nucleus  p +X
po  gg
p±  m± n
astrophysics
Observations in the 1990s of shell-type SNRs using groundbased instruments such as the Whipple telescope in Arizona
proved negative.
Buckley et al., A & A, 329, 639 (1998)
RXJ1713.7-3946 – first TeV image
 Acceleration of
primary particles
in SNR shock to
well beyond 100
TeV
Index ~ 2.1 – 2.2
Little variation across
SNR
Cutoff or break at high
energy
Aharonian et al., Nature, 75, 432 (2004)
Image from 2004 with all four
H.E.S.S. Phase telescopes; 2 arcmin
resolution, 33 hours livetime.
Enomoto, R. et al.,Nature, 416, 823-826 (2002)
Primary population: e or p ?
Electron model
B ~ 10 mG
• Need about 10 mG
B field to match
flux ratios
• Simplest electronic
models don’t work
well
Galactic Plane Scan
Microquasar LS 5039
compact 4 (?) M object in eccentric 4 day orbit
around 20-30 M star
closest approach ~1012 cm or ~2 stellar radii
Paredes J. M. et al.,
A&A 2002
RA (mas)
fuelled by wind accretion(?)
H.E.S.S. Results
with more data …
PSR B1259-693/SS2883
Be Star
Predicted by Kirk et al. (Astropart. Phys.,
10, 31, 1999 ) to emit VHE gamma rays
around periastron. Trouble is, periastron
occurs only once every 3.5 years
Pulsar
Artist view of the binary system PSR B1259-63/SS2883
48 ms pulsar in a highly
eccentric orbit around a B2e
star. At periastron, pulsar is
only ~1013 cm from its
companion.
IC losses
dominant
HESS J1303-631
It’s extended, it’s 21 after ~ 48.6hr livetime, it has a hard
spectrum…and no radio or X-ray counterpart.
843 MHz SUMSS radio map; X-ray
sources and radio sources (pulsars, HII
regions etc.) marked.
What is HESS J1303-631? PWN?
GRB remnant?
Atoyan et al., astro-ph/0509615
More Example Problems
Aharonian et al., Ap.J. 636, 777 (2006)
Galactic Centre
Detections of VHE gamma rays from the galactic centre have
been reported from both the CANGAROO II and Whipple
groups.
Kosack et al., Ap. J., 608, L97 (2004).
Tsuchiya et al., Ap. J., 606, L115 (2004)
H.E.S.S. observations show a source which is consistent with
the position of Sgr A* and with a nearby SNR. Significance
with 2004 data > 30
Sgr A*
H.E.S.S.
Position
Aharonian et al., Astron. Astrophys., 425, L13 (2004)
The H.E.S.S. spectrum is harder
that that observed with
CANGAROO. It also probably
rules out WIMPs with masses <
12 TeV being a significant
contributor to the flux from the
galactic centre. Is it the BH or is it
a SNR? Spectral index (2.2) is
consistent with a SNR origin.
Dark matter annihilation?
-11
E2F(E) [TeV/cm2s]
10
proposed
based on early
H.E.S.S. data
10-12
20 TeV Neutralino
20 TeV KK particle
10-13
0,1
1
E [TeV]
Bergström et al, Phys. Rev. Lett., 94, id. 131301 (2005)
proposed before
H.E.S.S. data
10
H.E.S.S. Observations of Diffuse
Emission in GC Region
Aharonian et al., Nature, 439, 695 (2006)
Active Galactic Nuclei
Object
Z
Discovery
Confirmation
Mkn 421
0.031
Whipple
Many!
Mkn 501
0.034
Whipple
Many!
1ES 2344+514
0.044
Whipple
HEGRA
PKS 2155-304
0.117
Durham
H.E.S.S., CANGAROO III
1ES 1959+650
0.047
7 TA
Whipple, HEGRA, MAGIC
H 1426+28
0.129
Whipple
HEGRA
M87
0.004
HEGRA
H.E.S.S.
PKS 2005-489
0.071
H.E.S.S.
1H 2356-309
0.165
H.E.S.S.
1ES 1101-232
0.186
H.E.S.S.
1ES 1218+304
0.182
MAGIC
PG 1553+113
> 0.25
H.E.S.S.
Mkn 180
0.045
MAGIC
BL Lacertae
0.069
MAGIC
MAGIC
VHE Emission from BL Lacs
The VHE emitters (so far) are the HBLs, where the synchrotron peak is in the
UV/X-ray region. The currently favoured model is the SSC model, but others,
including EC and proton-acceleration models, are proposed.
EBL Interactions
VHE photons will interact with the
EBL (in fact, the IR background)
via pair production.
g  g  e  e
This effect becomes stronger
with increasing distance and
photon energy.
At one level, this is a
disadvantage – the most
easily detected are the closest
objects.
On the other hand, it’s a good
way of measuring the EBL.
Mkn 421
~ 7000 gamma rays detected in 14.7
hours (EGRET detected a total of
5134 gammas from the Crab over its
~8 year lifetime)
Average rate 8 min-1
Overall significance > 100
E > 1.5 TeV (60-65° z.a.)
Average integral flux above 10 TeV ~
2x Crab
Changes in diurnal flux by up to a
factor of 4.5
PKS2155-304 in 2006
Preliminary
WOW!
In late July 2006, this AGN went crazy, and produced a burst that made the
object 20 times brighter than the Crab Nebula. The burst contained over
60,000 gamma rays!
Active Galactic Nuclei
Object
Z
Discovery
Confirmation
Mkn 421
0.031
Whipple
Many!
Mkn 501
0.034
Whipple
Many!
1ES 2344+514
0.044
Whipple
HEGRA
PKS 2155-304
0.117
Durham
H.E.S.S., CANGAROO III
1ES 1959+650
0.047
7 TA
Whipple, HEGRA, MAGIC
H 1426+28
0.129
Whipple
HEGRA
M87
0.004
HEGRA
H.E.S.S.
PKS 2005-489
0.071
H.E.S.S.
1H 2356-309
0.165
H.E.S.S.
1ES 1101-232
0.186
H.E.S.S.
1ES 1218+304
0.182
MAGIC
PG 1553+113
> 0.25
H.E.S.S.
Mkn 180
0.045
MAGIC
BL Lacertae
0.069
MAGIC
MAGIC
Spectra & ExtragalacticBackgroundLight
Source
spectrum
EBL
G = 1.5
1 ES 1101
G = 2.9±0.2
H 2356 (x 0.1)
G = 3.1±0.2
Preliminary
Spectra & ExtragalacticBackgroundLight
Source
spectrum
too
much
EBL
1 ES 1101
G = 2.9±0.2
H 2356 (x 0.1)
G = 3.1±0.2
Preliminary
 Upper limit
on EBL
Spectra & ExtragalacticBackgroundLight
UV
EBL
Not really
a solution:
add huge
amount
of UV photons
to EBL
too
much
EBL
1 ES 1101
G = 2.9±0.2
H 2356 (x 0.1)
G = 3.1±0.2
Preliminary
 problems
with
source
energetics,
X-ray/gammaray
SED ratio
Spectra & ExtragalacticBackgroundLight
X
measurements
upper
limits
EBL resolved
Universe more
transparent
X
HESS limits
lower limits
from galaxy
counts
Reference shape
Active Galactic Nuclei
Object
Z
Discovery
Confirmation
Mkn 421
0.031
Whipple
Many!
Mkn 501
0.034
Whipple
Many!
1ES 2344+514
0.044
Whipple
HEGRA
PKS 2155-304
0.117
Durham
H.E.S.S., CANGAROO III
1ES 1959+650
0.047
7 TA
Whipple, HEGRA, MAGIC
H 1426+28
0.129
Whipple
HEGRA
M87
0.004
HEGRA
H.E.S.S.
PKS 2005-489
0.071
H.E.S.S.
1H 2356-309
0.165
H.E.S.S.
1ES 1101-232
0.186
H.E.S.S.
1ES 1218+304
0.182
MAGIC
PG 1553+113
> 0.25
H.E.S.S.
Mkn 180
0.045
MAGIC
BL Lacertae
0.069
MAGIC
MAGIC
So what next???
HESS II – a single, large
(600 m2) telescope.
Lower energy (10-20
GeV) in standalone
mode
Improved sensitivity at
higher energy in
coincidence mode
Unify European Efforts
MAGIC
VERITAS
CTA involves scientists from
Czech Republic
Germany
France
Italy
Ireland
UK
Poland
Spain
Switzerland
Armenia
South Africa
Namibia
…
H.E.S.S.
and from several communities
astronomy & astrophysics
particle physics
nuclear physics
about 250-300 scientists working
currently in the field will be
directly involved,
user community significantly larger
Cherenkov Telescope Array
One observatory with two sites, operated by one consortium
Main Aims of CTA
GLAST
-11
10
Crab
2
E x F(>E) [TeV/cm s]
E.F(>E)
[TeV/cm2s]
-12
10% Crab
10
MAGIC
-13
10
H.E.S.S.
1% Crab
-14
10
10
100
1000
E [GeV]
10
4
10
5
Main Aims of CTA
GLAST
-11
10
Crab
2
E x F(>E) [TeV/cm s]
E.F(>E)
[TeV/cm2s]
-12
10% Crab
10
MAGIC
The “quite
expensive”
line
-13
10
+ Improved angular
resolution
+ all-sky capability
H.E.S.S.
1% Crab
-14
10
10
100
1000
E [GeV]
10
4
10
5
Timeline
Spring 2007 Letter of Intent
Spring 2007 FP7 DS application
2007-2010 Design Study
Mid/End 2008 Proposal (design options)
End of FP7 period: TDR w/ implementation
choices
2009/2010: start production/installation
From ground-based experiments towards
a TeV gamma-ray observatory
Ex Africa semper aliquid novi
Pliny the Elder