The Cherenkov Telescope Array (CTA)

Transcription

1 The Cherenkov Telescope Array (CTA) The CTA Consortium1, represented by Andreas Reisenegger2 1 2 see observatory.org/consortium_authors/authors_2018_01.html for full author list Instituto de Astrofísica & Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile CosmoAndes, Pontificia Universidad Católica de Chile, Santiago, January 2018

2 What is CTA? International project to build the largest (by far) high-energy gamma-ray observatory in the world Open, proposal driven observatory (not experiment ) Expected to generate 180 PB ( bytes) of data by 2030 E ~ 20 GeV TeV: interesting for astrophysics, fundamental physics, & their intersection: «astroparticle physics»

3 CTA Science Consortium 32 countries, 210 institutes, >1350 scientists & engineers

4 Locations Science data management center CTA North array site (19 telescopes) Headquarters CTA South arraysite (99 telescopes)

5 ACT, CLASS, POLARBEAR, Simons Obs., TAO, CCAT VLT, E ELT, CTA South CTA-South & other observatories in the Atacama desert (Chile) GMT LSST Thanks to Luis Chavarría, CONICYT Astronomy Program

6 CTA in the electromagnetic spectrum

7 Imaging Atmospheric Cherenkov Telescopes (IACTs)

8 2 arrays, 3 telescope sizes LSTs: 23 m (4 N + 4 S) lowest energies MSTs: 12 m (15 N + 25 S) intermediate energies SSTs: 4 m (70 S) highest energies (low gamma flux requires large area)

9 Different telescope designs & prototypes LSTs artistic rendering Prototype being built on La Palma site MST prototype in Berlin SCT Whipple Obs., Arizona SST 1M prototype in Krakow SST 2M ASTRI prototype in Serra La Nave, Italy SST 2M GCT prototype in Meudon, France

10 CTA timeline (under revision)

11 Flux sensitivity (point sources) High flux: detectable ~ few photons/km 2 /hour Low flux: not detectable

12 Angular resolution Moon s apparent radius 3 arcmin

13 Recent paper arxiv: More information and updates at observatory.org

14 CTA science themes Understanding the Origin and Role of Relativistic Cosmic Particles ( cosmic rays ) Cosmic Accelerators Propagation and Influence of accelerated particles Probing Extreme Environments Black holes and jets Neutron stars and relativistic outflows synergy with LIGO/VIRGO Cosmic voids Exploring Frontiers in Physics Dark Matter Quantum Gravity (Lorentz-invariance violation) Axion-like Particle Search of interest to astronomers & particle physicists Specially in Chile: multiwavelength/multimessenger studies

15 Some examples of CTA science

16 Cosmic rays VHE/UHE cosmic ray spectrum C. Patrignani et al. (Particle Data Group), Chin. Phys. C, 40, (2016) and 2017 update LHC Charged particles deflected by cosmic magnetic field do not point back at sources sources largely unknown can be probed by VHE gamma rays

17 Imaging cosmic-ray sources CTA should distinguish whether the main ingredient of the cosmic rays in supernova remnants are leptons or hadrons Simulated CTA images of the supernova remnant RXJ : (a) Dominated by electrons (b) Dominated by hadrons (c) Difference (black contours are H.E.S.S. observations)

18 H.E.S.S. view of the Galactic Center Gamma rays up to 40 TeV PeV protons interacting with gas clouds Unknown origin CTA will probe this region with much improved sensitivity and angular resolution H.E.S.S. VHE gamma ray view of the Galactic Center (2 4 degrees) (reproduced from Aharonian et al. (2006) Nature 439, 695) Top: Original image. Bottom: Dominant sources subtracted; ridge matches morphology of cold gas (white contours).

19 Probing dark matter (DM) particles Strong evidence for DM from astronomical observations (essential ingredient of cosmology): only collective gravitational effects Particle nature unknown; probe through: Colliders (LHC) Direct detection Indirect detection: mutual annihilation or spontaneous decay of DM particles standard model particles VHE gamma rays Targets: Galactic center/halo, dsph galaxies, LMC, galaxy clusters Number of VHE gamma ray events expected from DM annihilation

20 Dark matter: sensitivity to WIMP annihilation excluded region Thermal relic from Big Bang Assumptions: W + W annihilation Einasto DM profile CTA 500 hr observations Statistical errors only allowed region Solid lines: upper limits on the velocity weighted annihilation cross section placed by each experiment observing a certain cosmic source. Dashed line: required cross section if DM is a thermal relic WIMP from the Big Bang.

21 Dark matter: spontaneous decay time (Perseus cluster of galaxies) allowed region 10 9 Hubble times!! DM particle decay lifetime excluded region Lower limits on DM particle decay times (assuming bb or τ+τ channels): Fermi satellite observations of the halo of our Galaxy (dotted) 300 hour CTA observations of the Perseus cluster of galaxies (solid)

22 Propagation of VHE gamma rays Transients (GRBs, blazars) at cosmological distances precise measurement of photon speed as function of energy Lorentz invariance violation, quantum gravity effects Interaction with extragalactic background light (EBL) e + e pairs Suppression of flux from distant sources Echoes/halos of secondary gamma rays Heating of voids suppression of dwarf galaxy formation? Effects potentially reduced by temporary conversion of gamma rays into axion like particles in the intergalactic magnetic fields

23 Axion-like particles (ALPs) Parameter space probed by different experiments Expected ALP effect on the spectrum of a strong flare of the active galaxy 4C Sánchez Conde et al. (arxiv: )

24 Conclusions CTA will be the first true observatory of VHE gamma rays, open to guest observer proposals Breakthrough comparable to ALMA in mm waves Addresses several important astrophysics and fundamental physics questions Complementary to accelerators, neutrino & DM particle detectors, LIGO/VIRGO, & observatories across the electromagnetic spectrum Huge opportunity for the world and specially for Chile as host country of CTA-South