The Cherenkov Telescope Array project: Present situation at the Paris Observatory Hélène Sol LUTH, CNRS, Observatoire de Paris (OP) Meeting «CTA et la Science au TeV» à l Observatoire de Paris, Nov 28-29, 2013
The emergence of the Very High Energy (VHE) gamma-ray astronomy Previous generation: Whipple (US), Hegra (G, S, I), CAT/Celeste (F) OP started collaboration with CAT/Celeste (on AGN) Current generation: HESS, MAGIC, VERITAS, OP member of HESS since 2002: PHE team of LUTH (on AGN) + contribution to HESS 2 (OP) Number of confirmed VHE sources over years Towards > 1000 VHE sources with CTA Next generation: the global CTA project OP present from the very first mention in 2005
Implication of the OP teams in CTA 1 st discussion to propose a next generation international VHE project to the ESFRI at the conference in Palaiseau («Towards a Network of Atmospheric Cherenkov Detectors», April 2005), Design Studies (2006-2009), Preparatory Phase (2010-2014). Sciences & AGN Building prototypes for CTA Telescope structure Data, VO and Science User Group
Sciences and AGN LUTH team: conveners of the AGN-Working Group during the CTA-PP A. Zech: co-convener of the new «Extragalactic Group» Sciences with CTA and AGN Statistical studies of samples of various AGN types: detection of ~70 AGN in < 2 months (now: 55), ~170 AGN in ~3 years, 200-300 AGN in ~10 years. AGN and jets physics (see talk by Andreas) Search for extended emission around the compact sources AGN as beacons: probe the extragalactic space (Extragalactic Background Light, InterGalactic Magnetic Field) New physics: search for axion-like particles, for Lorentz Invariance Violation
One example : the BL Lac OJ 287, a possible binary massive Black Hole OVV with a remarkable 12-year period, possibly due to orbital period of BBH. Jet seen in radio and X-rays. CTA should monitore the VHE emission from the jet base at various orbital phases. A unique laboratory for jet formation study New outburst expected in 2017.
A 2 nd example: Probing the InterGalactic Magnetic Field VHE AGN Primary TeV photons Soft bckgrd photons from EBL and CMB e + e + e + e e + - e - e + e - e - e - Secondary GeV photons TeV Observer Cascades secondary GeV flux, dependent of the IGMF properties - Extended GeV emission around primary TeV signal - Delay of secondary GeV emission Lack of detection so far provided first non-zero lower limits on the IGMF! Origin of the magnetic field in the universe
Building prototypes for CTA: the GATE project Support by region «Ile-de-France», CNRS and CEA, coordination and support by the Paris Observatory (2010-2014) -Mechanical & thermal demonstrator of MST camera -Detection system based on NeCTAr modules, for NectarCAM -Array of scintillators, test clock distribution and central trigger -Structure of a S-C small size telescope -Energy module and mirrors (GATE budget: 800 k for equipment, about 50 people involved) LPNHE: elec camera IRFU: Module and mirrors LLR: meca camera APC: trigger LUTH/OP: SST
The mechanical demonstrator of MST camera (LLR, Polytechnique) Delivery, mounting and tests on the MST prototype at DESY in Zeuthen/Berlin since May 2013.
Modular and autonomous detection system (LPNHE, Jussieu) Mechanical structure for the first seven NeCTAr modules, in the perspective of NectarCAM that CEA and IN2P3 propose for MST (and LST) cameras for the CTA array.
Clock distribution and central trigger (APC, Paris 7) Successful tests of the clock distribution for the central trigger: Left: Measure of the propagation time of the signal as a function of time, and histogram. Right: Comparison of differences in dates measured by the dating system «MUTIN» developed at APC and a TDC.
The SST-GATE telescope in Meudon See the talk by Delphine Dumas (GEPI) Camera Mirror M1 Dish M1 Mast and Truss Structure MTS Mirror M2 Counterweight Elevation Structure Fork Azimuth Structure Tower Collaboration with UK teams, IRFU CTA Meeting - Chicago 11 In collaboratioinn for M2, and Italy with for future common SST design May 28 th June 1 st, 2013
Two S-C SST prototypes currently under construction in France and in Italy On-going collaboration towards a common SST proposal for SST array SST-GATE ASTRI
Data, Virtual Observatory and Science User Group C. Boisson: coordination of the WP-Data format (2009 2012) and of the SUG, Science User Group (since 2012 ) SUG: represents the CTA end user, the user point of view Ensures that the development of CTA designs, procedures and organisation are consistent with the needs and expectations of internal and external scientific users Strong links with : Physics, Observer access, Archives, and Observatory organisation.
Key areas for SUG Check requirements for data and analysis software, by use cases Software testing and evaluation processes, from Data Levels DL0/3 to DL5 Data rights /policy issues: proprietary time, handling of projects spread over more than one observation, wide field (rights on FoV sources?), verification phase data Archives: which ones, how to optimize. Interface to data (VHE data model): Work in collaboration with IVOA developer (Strasbourg, Madrid). Mid- to high-level data and metadata description to be compatible with the VO discussed at the interoperability meeting in Hawaii (September 2013)
Key areas for SUG Requirements for access to observing time: identifies and tests tools for source visibility, observation time simulator, expected sensitivity, proposal handling Various specific observing modes: how to handle them? - Alerts and targets of opportunity - Physics with sub-arrays: which strategy for which science? Provide sensitivity curves to general observers. - Surveys and diverging pointing - Moon light observations Beyond coordination, there is a lot of work to be done urgently! These works will be done, either at OP if manpower is available, or somewhereelse in the CTA teams.
A garanteed scientific return in several astrophysical and cosmological fields High discovery potential in fundamental physics Several possible synergies with research fields at the OP.
New physics: search for axion-like particles? Axions, hypothetical low mass particles: candidates for DM, convert into photons in presence of non-zero IGMF. Such «axion-photon» mixing effect can distort the VHE spectra of high-z sources. Their existence (if any) should modify our current interpretation of VHE extragalactic observations, and could provide interesting explanation in case of growing inconsistency with the standard views. One example: (Sol, Zech, Boisson, et al, 2013) Increasing statistics with CTA will clarify the trend of observed photon index versus redshift z. Should be an increasing function of z following standard view (due to EBL), but not yet firmly detected, possibly hidden by various observational biases.
New physics: search for Lorentz Invariance Violation? Quantum gravity models possibility of energy dependence of the speed of light in vacuum (~ space-time distorsion) velocity dispersion for massless particles at E ~ E Planck : c 2 p 2 = E 2 (1 ±ξ 1 (E/E P ) ±ξ 2 2 (E/E P ) 2 ± ) Induced time delay between 2 photons with a difference in energy of E t ~ ( E / ξ α E P ) α (L/c), where L is the distance of propagation Fermi with a GRB and HESS with a blazar: best constrain the linear and quadratic term with no time delay detection so far Requires a large sample of variable sources, AGN and GRB, at various z to disentangle intrinsic and propagation effects
The diffuse VHE background Origin of the extragalactic gamma-ray background (EGRB)? Contribution from unresolved sources as AGN, + galaxies, starbursts, diffuse IGM, pair halos, DM? Detection by Fermi below 100 GeV: ~ 70% of EGRB possibly explained by known populations 30% may be new populations, or systematic uncertainties in measurement (foregrounds ) Set an upper limit on the EGRB above 100 GeV (considering cascades on low-frequency backgrounds), below the Fermi data points! Studying the EGRB with CTA to solve such inconsistency. New physics? New populations? Search for turnover above 100 GeV due to EBL absorption Y. Inoue Real challenge