VHE Astrophysics with VERITAS VERITAS Tel 2 Tel 1 Tel 4 Tel 3 Rene A. Ong Caltech/Kellogg Seminar 29 Feb 2008
Outline Scientific Motivation A New Astronomy Physicist s Viewpoint Astrophysical TeV accelerators Origin of Cosmic Rays Probes of new physics, cosmology Experimental Technique The VERITAS project Description, operation, & performance Results from first year of operation Science program 2008-2012 Future Prospects GLAST & AGIS Rene A. Ong 29 Feb 2008 Caltech Page 2
A New Astronomy Before 1940 s Astronomy only used visible light. New wavebands (radio, IR, X-ray, γ-ray) change our picture of the universe Different spatial scales Radio Optical X-rays Different time scales Crab Nebula Different emission processes New physics Crab Nebula Other messengers (cosmic rays, neutrinos, grav. waves) TeV γ-rays Rene A. Ong 29 Feb 2008 Caltech Page 3
New Windows & New Messengers Messengers Cosmic Rays --------------------- Neutrinos ------------------------ Radio IR O UV X-rays γ-rays ---------------------------- Log Frequency (Hz) 9 12 15 18 21 24 27 30 33 THERMAL UNIVERSE NON-THERMAL UNIVERSE -6-3 0 3 6 9 12 15 18 21 Log Energy (ev) HE VHE UHE --- Crab Nebula Gamma-Ray Bursts (GRBs) Active Galactic Nuclei (AGN) Dark TeV Accelerators PeV ν s >10 19 ev Particles Rene A. Ong 29 Feb 2008 Caltech Page 4
The TeV γ-ray Sky - 1995 3 sources Mrk421 Mrk501 Crab Pulsar Nebula SNR AGN Other, UNID Rene A. Ong 29 Feb 2008 Caltech Page 5
The TeV γ-ray Sky - 2003 12 sources Mrk421 H1426 M87 Mrk501 1ES1959 Cas A 1ES 2344 TeV 2032 RXJ 1713 GC Crab PKS 2155 Pulsar Nebula SNR AGN Other, UNID Rene A. Ong 29 Feb 2008 Caltech Page 6
The TeV γ-ray Sky - 2006 30+ sources Mrk421 H1426 1ES 1218 1ES1959 Cas A 1ES 2344 Cygnus Diffuse TeV 2032 Mrk501 SNR G0.9 LS 5039 PKS 2155 M87 RXJ 1713 GC H2356 PSR B1259 MSH 15-52 PKS 2005 1ES 1101 RXJ 0852 Vela X HessJ1303 Crab Pulsar Nebula SNR AGN Other, UNID Rene A. Ong 29 Feb 2008 Caltech Page 7
The TeV γ-ray Sky - 2008 http://tevcat.uchicago.edu/ >50 sources AGN Shell Type Supernova Pulsar Wind Nebula Radio Galaxy X-ray Binary UNID Explosion in number of sources. Discovery of numerous source classes. Almost all discoveries made by Atmospheric Cherenkov Telescopes HEGRA Whipple detected first sources: Crab, AGN 2008: New Cherenkov arrays have now seen ~50 sources, mostly Galactic. Rene A. Ong 29 Feb 2008 Caltech Page 8
High-Energy Neutrino Sky No sources yet. Rene A. Ong 29 Feb 2008 Caltech Page 9
A Wide Variety of Sources Supernova Remnants Pulsars/PWN HMXBs (microquasars) Active Galactic Nuclei Shocks NS dynamo Winds Accretion-powered jets, colliding winds, or? Jets Gamma-Ray Bursts Dark accelerators Massive star collapse Int./ext. shocks???... and accelerators Rene A. Ong 29 Feb 2008 Caltech Page 10
Putting the zoo to work SNR Origin of cosmic rays AGN? Cosmological γ-ray horizon GRBs Tests of Lorentz invariance Low E High E Cold dark matter (WIMP) searches Galactic Center Rene A. Ong 29 Feb 2008 Caltech Page 11
Origin of Cosmic Rays = SNRs? Why (VHE) gamma-rays? Unlike cosmic rays, not deflected by interstellar magnetic fields. Tracers of parent particle populations. Accelerated electrons VHE γ-rays Up-scattering of soft photons Accelerated protons VHE γ-rays Target interaction, π 0 decay p Target material π 0 γ γ SNR RXJ 1713-3946 Evidence for SNR acceleration of CRs, but case is far from settled. Spectral Energy Distribution Rene A. Ong 29 Feb 2008 Caltech Page 12
AGN Active Galactic Nuclei High-luminosity extragalactic objects Probe properties of the universe at large distances Variable So far, AGN observed in VHE γ-rays are mostly: Blazars Jets aligned with line of sight Nearby: z < 0.2 Rene A. Ong 29 Feb 2008 Caltech Page 13
Extragalactic Background Light (EBL) Diffuse extragactic background light (how much light since recombination?) Complements direct measurment in Optical, IR: foregrounds. Indirect: absorption signature for distant sources. 2.7K Red shifted stellar light Red shifted dust light Rene A. Ong 29 Feb 2008 Caltech Page 14
Indirect Detection of Dark Matter Hypothesis: DM = WIMPs High WIMP density in certain locations. WIMP annihilation γ, ν etc. Galactic Halo Galactic Center ν,ν γ lines χ+χ γ continuum Point back to source p e + d Search for excess components in cosmic rays (Diffusion) (PAMELA,AMS,GAPS) Galactic Satellites Extragalactic Sources Complementary approach to direct detection & LHC. Key components of IDDM PFC Proposal: UCLA,UCI,Caltech. Rene A. Ong 29 Feb 2008 Caltech Page 15
The Galactic Center HESS Galactic plane HESS 22 error circle Galactic Center is a strong source of TeV γ-rays is it dark matter? Sgr A East SNR (radio) Sgr A* Rene A. Ong 29 Feb 2008 Caltech Page 16
Experimental Technique Rene A. Ong 29 Feb 2008 Caltech Page 17
Effective area =light pool size =10 5 m 2!!! Rene A. Ong 29 Feb 2008 Caltech Page 18
Whipple 10m Telescope The Whipple 10m (1968- ). Added Tracking and an Imaging Camera. Increased the mirror area to ~100m 2. 10m gamma ray? cosmic ray? Rene A. Ong 29 Feb 2008 Caltech Page 19
Stereoscopy: Telescope Arrays Rene A. Ong 29 Feb 2008 Caltech Page 20
Major New VHE Telescopes MAGIC GLAST (2008) VERITAS (Auger, CR s) HESS IceCube, ν s (2011) CANGAROO Rene A. Ong 29 Feb 2008 Caltech Page 21
VERITAS Collaboration of ~80 scientists. 15 Institutions in U.S., Canada, U.K., and Ireland. Spokesperson: S. Swordy D. Spokesperson: R. Ong Detector Design: Four 12m telescopes. 500 pixel cameras (3.5 o ). Site in southern Az (1300m). Performance: Energy threshold ~ 100 GeV. Ang. resolution ~ 4-6. Detect Crab Nebula in ~45s. Rene A. Ong 29 Feb 2008 Caltech Page 22 Very Energy Radiation Imaging Telescope Array System (VERITAS)
Bumps in the Road VERITAS had three major road-blocks: 1998 Project formally proposed 2000 Ranked highly in Decadal Survey 2001 First Major Review (Ritz) Smithsonian forced to reduce funding 2003 Second Major Review (Blandford) Unable to secure site on Mt. Hopkins Invited to Kitt Peak (NSF/NOAO) 2004 Construction starts 2005 Telescope 1 operational at basecamp. Lawsuit regarding Kitt Peak site 2006 Telescope 2 & 3 at Whipple basecamp. 2007 4 Telescope array fully operational! 2008 VERITAS sited permanently at basecamp. Rene A. Ong 29 Feb 2008 Caltech Page 23
VERITAS-4 at the Whipple Observatory VERITAS April 2007 F.L. Whipple Basecamp Mt. Hopkins, AZ (1300m a.s.l.) T2 T1 T4 T3 First Light Celebration, 04/28/07 Rene A. Ong 29 Feb 2008 Caltech Page 24
VERITAS-4 at the Whipple Observatory Telescope Layout Fall 2006 T3 109 m T2 Since January 2006 85 m 85 m T4 35 m T1 March 2007 Rene A. Ong 29 Feb 2008 Caltech Page 25
Telescope and Camera 12m reflector, f1.0 optics 500 pixel Camera Rene A. Ong 29 Feb 2008 Caltech Page 26
VERITAS Data Acquisition PMTs digitized with 500 MHz sampling FADCs 24 samples/channel. <6% deadtime @ 250 Hz. Telescopes meet all specifications. Rene A. Ong 29 Feb 2008 Caltech Page 27
Telescope 1 Movies γ-ray Rene A. Ong 29 Feb 2008 Caltech Page 28
Telescope 1 Movies Cosmic Ray Rene A. Ong 29 Feb 2008 Caltech Page 29
Telescope 1 Movies Muon Ring Rene A. Ong 29 Feb 2008 Caltech Page 30
VERITAS-4 at the Whipple Observatory Typical 4 Telescope Event Core position on ground. Rene A. Ong 29 Feb 2008 Caltech Page 31
VERITAS-4 at the Whipple Observatory VERITAS Performance I Single Telescope Theta square plot (Wobble) Event counts 5000 4500 4000 Crab Source Background 3500 T1+T2 3000 (Wobble) 2500 2000 1500 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2 θ [deg ] θ 2 ~4 p.e. 3 - Telescope, 100ns T1+T2+T3 Three Level Trigger (single PMT) L1 CFD (4 p.e.) L2 Telescope (pattern) L3 Array (~ 150 Hz) Angular Resolution 2, 3 Telescope Crab Data Single γ resolution < 0.1 o Rene A. Ong 29 Feb 2008 Caltech Page 32 θ 2
Crab Nebula Now a Calibration! 1 Crab 90s (5σ) 10% Crab ~1 hr 3% Crab ~10 hrs Energy spectrum 3 telescope array: Γ=-2.43±0.05, F(E>1 TeV)=(3.1±0.16)x10-7 m -2 s -1 significance ~35 σ/ hour for three telescope array (8 γ/min) Rene A. Ong 29 Feb 2008 Caltech Page 33
First-Year VERITAS Detections Chandra IC443 J0617 Be T=26.5 days HST M87 Chandra Crab Nebula SNR IC 443 XRB LSI +61 M87 Radio Galaxy SNR Cassiopeia A Blazar Mrk 421 z=0.03 Blazar 1ES1218+30 z=0.182, 2 nd most distant VHE blazar And. Blazar 1ES 2344+514 Blazar Mrk 501... Rene A. Ong 29 Feb 2008 Caltech Page 34
VERITAS-4 at the Whipple Observatory Microquasar LSI +61 303 HMXB located at 2 kpc distance Be Star coupled with NS 26.5 day orbital cycle LSI61-0.63< Ψ <0.71 Period = 26.5 days Crab Spot mean rate VERITAS 3 Telescopes 8.3 hrs, 7.1σ, 7% Crab VERITAS Rate versus orbital phase. Rene A. Ong 29 Feb 2008 Caltech Page 35
LSI +61 303 HE Emission Rene A. Ong 29 Feb 2008 Caltech Page 36
Key Science Projects SKY SURVEY SNRs/PWN BLAZARS VERITAS DARK MATTER Rene A. Ong 29 Feb 2008 Caltech Page 37
Supernova Remnants (SNRs) RX J0459+515 (G156.2+5.7 Tycho Cas A Gamma Cyg IC 443 Rene A. Ong 29 Feb 2008 Caltech Page 38
382, 303 (2003) h/0705.3119v1 s et al. Phys. Rep. 3 Albert et al. astro-ph Figures from Torres MAGIC point from A Discovery of SNR IC 443 EGRET source (overlaps remnant) MAGIC Black optical White EGRET Color - CO + Crab Nebula IC 443 Discovered by MAGIC and VERITAS VHE source position agrees with interaction zone of molecular cloud. VERITAS observation/detection ~16 hours of data (3-tel. array) 7.1 σ detection Flux F(E>200 GeV) ~3% Crab Flux Consistent with MAGIC s 5.7 σ detection in 29 hrs. Rene A. Ong 29 Feb 2008 Caltech Page 39
VERITAS Sky Survey 2007 2008 2 year program: survey of Cygnus region ( -1 < b < 4 and 52 < l < 82 ) Many targets of interest (SNRS, PWN, EGRET sources, X-ray binaries, VHE sources). Discovery potential (dark accelerators in particular). Rene A. Ong 29 Feb 2008 Caltech Page 40
Observation Strategy, Status 1 Makes full use of 17cameraFOV 1.7 0.8 Observations began in April 2007 Crucial: Understand our sensitivity Keep trials factors low Follow-up strategy Optimizing analysis strategy before opening the box. Rene A. Ong 29 Feb 2008 Caltech Page 41
What s next for VERITAS? LOTS! Observing: we are in first year of 5+ year program. Spectra and modelling: source mechanisms. Images: extended sources (SNRs, PWN, etc.). MWL studies: radio, optical, X-ray, γ-ray. GLAST overlap: alerts, calibration, science. Upgrade possibilities: e.g. new cameras. Crab Nebula Rene A. Ong 29 Feb 2008 Caltech Page 42
FUTURE PROSPECTS Next 5-10 years will be exciting period for this field: VERITAS will survey the northern TeV sky with great sensitivity, complementing: GLAST (GeV, in space) HESS (TeV, S. Hemisphere) IceCube (ν, South Pole) Farther in the future: Astrophysics at GeV & TeV energies with large km 2 Cherenkov Telescope arrays. Rene A. Ong 29 Feb 2008 Caltech Page 43
GLAST Satellite Telescope GLAST LAT Instrument: Si-strip tracker CsI calorimeter Anti-coincidence veto GLAST: Low E, wide FOV. VERITAS: High E, large sensitvity. Simulated sky map from 1 year survey. Launch in May 2008. Rene A. Ong 29 Feb 2008 Caltech Page 44
AGIS (Advanced Gamma Imaging System) AGIS: Large (1 km 2 )array array. ~50-75 telescopes, aperture 8-20m. Much more sensitive than GLAST/VERITAS. CTA project in Europe well underway. APS White Paper study. $100M class experiment. AGIS Concept 0.04-200 TeV, large FOV, 1 PSF per photon GLAST AGIS VERITAS 1.4 km Rene A. Ong 29 Feb 2008 Caltech Page 45
Future TeV Source Sensitivity HESS/VERITAS Simulation AGIS/CTA Simulation Rene A. Ong 29 Feb 2008 Caltech Page 46
Summary VHE particles provide unique tests of the limits of physical laws. Probe astrophysics in regimes not yet explored. Possibility for discovery of physics beyond our standard models. Exciting discoveries of many, unexpected sources of VHE gamma-rays. But still, most of the sky remains unexplored. VERITAS is now operational and getting exciting results. New Astronomy of TeV γ-rays and neutrinos should reveal many surprises over the next 5-10 years. The real voyage of discovery consists, not in seeking new landscapes, but in having new eyes. Marcel Proust (1871-1922) 1922) Rene A. Ong 29 Feb 2008 Caltech Page 47