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 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  R 0 / R(t) and therefore redshift and time are related by the lookback-time. Time (distance) vs redshift measures cosmology

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The Cherenkov Telescopes

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The Cherenkov Telescopes Previous Situation: –Energy gap between satellites ( 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 Telescopes The “Big” four Montosa Canyon, Arizona Roque de los Muchachos, Canary Islands Windhoek, Namibia Woomera, Australia MAGIC (2004) HESS (2003) CANGAROO III VERITAS

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The Cherenkov Telescopes Image 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 Altitude (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 MAGIC Telescope

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 diameter Image Air Cerenkov 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 tubes 65 ton total weight Frame corrected using Active Mirror Control 3.5° FOV camera 577 pixels Optical fiber analogic transmission 2 level trigger & 300 MHz FADC

Seminari IEEC - 15-XII-04Oscar Blanch Bigas 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)

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The MAGIC Telescope The Reflector Tessellated reflector: –~950 mirror elements –49.5 x 49.5 cm 2 –All-aluminum, quartz coated, diamond milled, internal heating –>85% reflectivity in nm Active mirror control: Use lasers to recall panel positions when telescope moves

Seminari IEEC - 15-XII-04Oscar Blanch Bigas 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,...

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The MAGIC Telescope

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The MAGIC Telescope Signal 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: DAQ: Continuous ~700 Hz

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The MAGIC Physics

Seminari IEEC - 15-XII-04Oscar Blanch Bigas The MAGIC Physics Dark Matter Pulsars GRBs Quantum Gravity 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 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. The group of pairs (E,z) for which is defined as the Gamma Ray Horizon (GRH) (Fazio-Stecker relation). High energy  -rays travelling cosmological distances are expected to be absorbed through their interactions with the EBL by: Optical Depth & Gamma Ray Horizon

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Optical Depth & Gamma Ray Horizon GRH for a specific scenario: Transparent region For each source (fixed redshift) the GRH energy (E 0 ) is defined as the energy on the GRH. source GRH energy Opaque region

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Optical Depth & Gamma Ray Horizon Influence of the Cosmological Parameters The Hubble constant: H 0 =72  4 Km s -1 Mpc -1 (Spergel et al, 2003) look-back time Similar shift (10% at 3  Ho ) over the whole redshift range

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Optical Depth & Gamma Ray Horizon The cosmological densities:  m =0.29  0.07,  =0.72  0.09 (Wang et al, 2003) 0% variation at z=0 10% and 5 % at z=4 m astro-ph 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 H 0 =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 & E ) –Egret Sources extrapolation Flux extrapolation (source model & data, Optical Depth, Culmination angle, MAGIC, 50h)  Fit to

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 Cosmological Measurements

Seminari IEEC - 15-XII-04Oscar Blanch Bigas 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

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 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

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Cosmological Measurements Estimation of foreseen systematic errors Systematic error on GRH determination: Global energy scale: 15% Extragalactic Background Light:

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Cosmological Measurements Estimation of foreseen systematic errors Systematic error on GRH determination: Global energy scale: 15% Extragalactic Background Light:

Seminari IEEC - 15-XII-04Oscar Blanch Bigas 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 submited APh

Seminari IEEC - 15-XII-04Oscar Blanch Bigas Cosmological Measurements Comparison to current  m and  measurements: galaxy counting, Supernovae and Microwave. 15 % UV constraint30 % 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 % 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