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Cosmology with the New Generation of Cherenkov Telescopes. Oscar Blanch Bigas IFAE, UAB Seminari IEEC 15-XII-04. Introduction. INTRODUCTION. Cosmic Rays hit the Earth’s atmosphere ( 1000 m -2 s -1 ): What are their sources? What is their chemical composition? - PowerPoint PPT Presentation
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Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmology with the New Generation of Cherenkov
Telescopes
Oscar Blanch Bigas
IFAE, UAB
Seminari IEEC
15-XII-04
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Introduction
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
INTRODUCTION
• Cosmic Rays hit the Earth’s atmosphere (1000 m-2 s-1):– What are their sources?– What is their chemical composition?– What are the astrophysical process of the acceleration?– How do they propagate through galactic and extragalactic space?– …
more than 99% are charged particles …
but they loose original direction• CGRO & Whipple breakthrough on -ray astronomy (0.1%).
– Production processes of -ray might also be responsible for the production of the CR
• Light on Fundamental Physics: dark matter, antimatter, quantum gravity, cosmology, ...
-ray Astronomy
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
INTRODUCTION
• “Cosmological Principle”: homogeneous and isotropic universe.
Cosmology
2
12222
2
222 dsinrdr
kr
drtRdtds
• In the context of general relativity, the dynamics of the universe is governed by the Friedmann equation.
zzz)z(HHRR
mo 211 222
Where the redshift (z) is defined as: 1+z R0 / R(t) and therefore redshift and time are related by the lookback-time.
2
12
0 211
11
zzzzH
zdzdt
mTime (distance) vs redshift
measures cosmology
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The CherenkovTelescopes
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The Cherenkov Telescopes
• Previous Situation:– Energy gap between satellites (<10 GeV) and ground-based
Telescopes (>300 GeV).– Extinction of number of sources in this gap :
For extragalactic sources absorption due to Extragalactic Background Light (EBL).
New Generation of Cherenkov Telescopes
Satellites< 10 GeV
Ground-based> 300 GeV
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The Cherenkov TelescopesThe “Big” four
Montosa Canyon,Arizona
Roque de los Muchachos, Canary Islands
Windhoek, Namibia
Woomera, Australia
MAGICMAGIC (2004) (2004)
HESSHESS (2003) (2003)
CANGAROO IIICANGAROO III
VERITASVERITAS
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The Cherenkov TelescopesImage Air erenkov Technique
• IACT do not see the -ray hitting the atmosphere but the erenkov light from the electro-magnetic shower developed in the atmosphere (calorimeter with atmosphere as active material)
The light is collected and focused on the camera forming and image of the electro-magnetic shower.
The image may come from a pure electro-magnetic shower (,e-) or from the electro-magnetic part of hadron showers (p,He,…).
Fast -pulse allow to reduce background due to LONS
Alt
itu
de
(Km
)
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The Cherenkov Telescopes• The images formed by hadronic showers (background) and electro-
magnetic (signal) are different.
Photons point to the center! Protons do not!
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The Cherenkov Telescopes
s appear
Moreover, the shape is also different and it is usually described by Hillas Parameters:
(width, length, dist, alpha, ...)
They depend on energy of incident spectrum from each source.
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGICTelescope
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC Telescope
• MAGIC requests:– Lowering as much as possible the Energy Threshold.– Maximum feasible sensitivity in the unexplored energy range.– Extragalactic sources North Hemisphere.– Fast repositioning for GRB follow-ups Light Telescope.
17 m diam
eter
17 m diam
eter
Image Air
Image Air
Cerenkov Telescope
Cerenkov Telescope
@@
Roque de los Muchachos
Roque de los Muchachos
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC Telescope
• An advanced 17 m Telescope based on a series of innovative features.
A second Generation IACT - MAGIC
17m Ø mirror Ultralight alluminum panels 85%-90% reflectivity
Light carbon fiber tubes65 ton total weightFrame corrected using Active Mirror Control
3.5° FOV camera 577 pixelsOptical fiber analogic
transmission2 level trigger & 300 MHz FADC
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC TelescopeThe Frame
The largest telescope mirror ever built by Human Being: 240 m² surface.
Light weight carbon fiber structure.
17 tons : Dish + Mirrors
64 tons: Telescope
(fast positioning over 180 in 22s)
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC TelescopeThe Reflector
Tessellated reflector:– ~950 mirror elements – 49.5 x 49.5 cm2
– All-aluminum, quartz coated, diamond milled, internal heating
– >85% reflectivity in 300-650nm
Active mirror control: Use lasers to recall panel positions when telescope moves
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC TelescopeCamera and signal transmission
577 PMTsCoating & Double crossingInner zone: 396 pixels of 0.1Outer zone: 180 pixels of 0.2
Optical analogic transmitters160 m of fibres: short signal, optically decoupled, cable weigth,...
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC Telescope
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC TelescopeSignal Processing
Optical transmission over 162 m
1st Level Trigger: 2,3,4,5-fold next neighbour
2nd Level: freely programmable
300 MHz, 8 Bit FADC.
Dynamic range: 2000.
DAQ: Continuous ~700 Hz
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGICPhysics
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC Physics
Dark Matter
Pulsars
GRBs
Quantum Quantum Gravity effectsGravity effects
SNRs
AGNs
-RH & Cosmology
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
The MAGIC Physics
Active Galactic Nuclei refers to galaxies with a central region where high-energetic processes take place.
Active Galactic Nuclei
• AGN have been found in all wavelength and they showed emission up to TeV energies.
• Emission in jet produced by electron or proton primaries?
• Highest variability in X-ray and -ray.
• High energy -ray from very far distances: Cosmology, Quantum Gravity, ...
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth&
Gamma Ray Horizon
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Concept - EBL absorption
Optical Depth and GRH
ee
Then the -ray flux is attenuated while travelling from the emission point to the detection point.
The integration over the path travelled across the universe, which depends on the source redshift (z), is the Optical Depth.
zxEzx
dxzd
dtczd)z,E( ,,,,nd
m
z
2
00 2
The group of pairs (E,z) for which is defined as the Gamma Ray Horizon (GRH) (Fazio-Stecker relation).
z,Ee 0
High energy -rays travelling cosmological distances are expected to be absorbed through their interactions with the EBL by:
Optical Depth & Gamma Ray Horizon
1z)(E,
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth & Gamma Ray Horizon
GRH for a specific scenario:
Transparent regionTransparent region
For each source (fixed redshift) the GRH energy (E0) is defined as the energy on the GRH.
source
GRH ener
gy
Opaque regionOpaque region
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth & Gamma Ray Horizon
Influence of the Cosmological Parameters
•The Hubble constant: H0=724 Km s-1 Mpc-1 (Spergel et al, 2003)
2
12
0 211
11
zzzzH
zdzdt
m
look-back time
Similar shift (10% at 3Ho) over
the whole redshift range
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth & Gamma Ray Horizon
•The cosmological densities: m=0.290.07, =0.720.09 (Wang et al, 2003)
0% variation at z=0
10% and 5 % at z=4
m
astro-ph-0107582
submited APh
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth & Gamma Ray Horizon
MAGIC capability
• We assume an EBL model (Kneiske et al, 2004) and universe with H0=72 Km s-1 Mpc-1 , m=0.29 and =0.72.
• MAGIC characteristics from MC : Trigger Collection Area, Energy Threshold and Energy Resolution.
• The suitable -ray candidates: – Well known TeV emitters (Mkn421, Mkn501 & E1426+428)– Egret Sources extrapolation
• Flux extrapolation (source model & data, Optical Depth, Culmination angle, MAGIC, 50h) Fit to
)EEexp(E)E( 00
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Optical Depth & Gamma Ray Horizon
Despite simplification,
reasonable 2 and
Eo = 1-5%sta 1-5%sys
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
CosmologicalMeasurements
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsThe new method
The GRH energy depends on the Cosmology and the distance to the source A cosmological dependent distance estimator, which does not rely on standard candles.
Moreover, the GRH behaves differently as a function of redshift than other observables already used for cosmology measurements.
The GRH can be usedThe GRH can be usedas an independentas an independentmethod to measuremethod to measure
cosmological parameterscosmological parameters
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological Measurements
m=0.29, =0.72
Four parameters fit based on a multi-dimensional interpolating routine.
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsStatistic Precision for m &
An external constraint of 724 km/ s Mpc (Spergel et al, 2003) for the Hubble constant is used.
Expected contour of
68 %, 95% and 99%
confidence level
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsEstimation of foreseen systematic errors
• Systematic error on GRH determination:
• Global energy scale: 15%
• Extragalactic Background Light:
)EE(eE 00
e )E(s )E(
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsEstimation of foreseen systematic errors
• Systematic error on GRH determination:
• Global energy scale: 15%
• Extragalactic Background Light:
)EE(eE 00
e )E(s )E(
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsAbove redshift z0.1, the difference on the GRH come from UV background.– Fit only source with z > 0.1– Add one parameter to fit : UV
background level.
High Correlation
UV-m
External Constraints:
5,15,25,30 %
(50 %, Scott et al, 2000)
astro-ph-0406061
submited APh
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Cosmological MeasurementsComparison to current m and measurements: galaxy counting,
Supernovae and Microwave.
15 % UV constraint 30 % UV constraint
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
Conclusions
Seminari IEEC - 15-XII-04Oscar Blanch Bigas
• Precise Measurement of the GRH lead to a new technique to measure m and
– Independent from other techniques currently used.– No standard-candle ( but uniform and isotropic EBL )– Active Galactic Nuclei highest observable redshift
• The precision of this technique is dominated by the systematic due to the poor knowledge of the EBL. At least a 15-25 % precision on the UV background level is needed (currently 50%).
• MAGIC (as well as other Cherenkov Telescopes) already started to observe AGNs at large redshift (z>0.1).
How many are going to be seen?
• AGN are interesting by itself but any spectrum from an AGN will help to get cosmological information with this method.
Conclusions-Outlook