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Cosmology with the New Generation of Cherenkov Telescopes

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?

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Cosmology with the New Generation of Cherenkov Telescopes

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  1. Cosmology with the New Generation of Cherenkov Telescopes Oscar Blanch Bigas IFAE, UAB Seminari IEEC 15-XII-04

  2. Introduction

  3. 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

  4. INTRODUCTION “Cosmological Principle”: homogeneous and isotropic universe. Cosmology • In the context of general relativity, the dynamics of the universe is governed by the Friedmann equation. Where the redshift (z) is defined as: 1+z  R0 / R(t) and therefore redshift and time are related by the lookback-time. Time (distance) vs redshift measures cosmology

  5. The Cherenkov Telescopes

  6. 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 Ground-based > 300 GeV Satellites < 10 GeV

  7. The Cherenkov Telescopes The “Big” four MAGIC (2004) VERITAS Roque de los Muchachos, Canary Islands Montosa Canyon, Arizona HESS (2003) CANGAROO III Windhoek, Namibia Woomera, Australia

  8. The Cherenkov Telescopes 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) Image Air erenkov Technique 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 Altitude (Km)

  9. The Cherenkov Telescopes The images formed by hadronic showers (background) and electro-magnetic (signal) are different. Photons point to the center! Protons do not!

  10. The Cherenkov Telescopes 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. s appear

  11. The MAGIC Telescope

  12. 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 diameter Image Air Cerenkov Telescope @ Roque de los Muchachos

  13. 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 3.5° FOV camera 577 pixels Optical fiber analogic transmission 2 level trigger & 300 MHz FADC Light carbon fiber tubes 65 ton total weight Frame corrected using Active Mirror Control

  14. The MAGIC Telescope The 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)

  15. The MAGIC Telescope Tessellated reflector: ~950 mirror elements 49.5 x 49.5 cm2 All-aluminum, quartz coated, diamond milled, internal heating >85% reflectivity in 300-650nm The Reflector Active mirror control: Use lasers to recall panel positions when telescope moves

  16. The MAGIC Telescope Camera and signal transmission 577 PMTs Coating & Double crossing Inner zone: 396 pixels of 0.1 Outer zone: 180 pixels of 0.2 Optical analogic transmitters 160 m of fibres: short signal, optically decoupled, cable weigth,...

  17. The MAGIC Telescope Solarium Bed-room Kitchen W C

  18. The MAGIC Telescope 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 Signal Processing

  19. The MAGIC Physics

  20. The MAGIC Physics AGNs Dark Matter SNRs g-RH & Cosmology Quantum Gravity effects Pulsars GRBs

  21. 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 emissionup 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, ...

  22. Optical Depth & Gamma Ray Horizon

  23. Optical Depth & Gamma Ray Horizon Optical Depth and GRH Concept - EBL absorption High energy -rays travelling cosmological distances are expected to be absorbed through their interactions with the EBL by: The integration over the path travelled across the universe, which depends on the source redshift (z), is the Optical Depth. Then the -ray flux is attenuated while travelling from the emission point to the detection point. The group of pairs (E,z) for which is defined as the Gamma Ray Horizon (GRH) (Fazio-Stecker relation).

  24. Optical Depth & Gamma Ray Horizon GRH for a specific scenario: Opaque region GRH energy Transparent region source For each source (fixed redshift) the GRH energy (E0) is defined as the energy on the GRH.

  25. Optical Depth & Gamma Ray Horizon Influence of the Cosmological Parameters look-back time • The Hubble constant: H0=724 Km s-1 Mpc-1(Spergel et al, 2003) Similar shift (10% at 3Ho) over the whole redshift range

  26. Optical Depth & Gamma Ray Horizon • The cosmological densities: • m=0.290.07, =0.720.09 (Wang et al, 2003) m  0% variation at z=0 10% and 5 % at z=4 astro-ph-0107582 submited APh

  27. 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

  28. Optical Depth & Gamma Ray Horizon Despite simplification, reasonable 2 and Eo = 1-5%sta  1-5%sys

  29. Cosmological Measurements

  30. Cosmological Measurements The 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 used as an independent method to measure cosmological parameters

  31. Cosmological Measurements m=0.29, =0.72 Four parameters fit based on a multi-dimensional interpolating routine.

  32. Cosmological Measurements Statistic Precision for m &  An external constraint of 724 km/ s Mpc(Spergel et al, 2003) for the Hubble constant is used. Expected contour of 68 %, 95% and 99% confidence level

  33. Cosmological Measurements Estimation of foreseen systematic errors • Systematic error on GRH determination: • Global energy scale: 15% • Extragalactic Background Light:

  34. Cosmological Measurements Estimation of foreseen systematic errors • Systematic error on GRH determination: • Global energy scale: 15% • Extragalactic Background Light:

  35. Cosmological Measurements • Above redshift z0.1, 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

  36. Cosmological Measurements Comparison to current m and  measurements: galaxy counting, Supernovae and Microwave. 15 % UV constraint 30 % UV constraint

  37. Conclusions

  38. 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

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