VERITAS Performance Gernot Maier Alliance for Astroparticle Physics
What scientific impact will VERITAS have in the next 3-5 years? Galactic long-term plan Performance Operations LTP & Performance May 214 2
The next few years at very-high energies 7 y) 2 rra a l l u f 1 2 w no 7 ( mirror alignment T1 move 2,3-telescope operations HESS trigger upgrade camera upgrade Fermi MAGIC II HESS II HESS I camera upgrade MAGIC HAWC MILAGRO LTP & Performance May 214 17 d2? n e ay t A n CT ume h Arr t r r t s o in? N e tiv 2 i s n y2 e s 3 arra t s mo ull? 1 2 8
VERITAS: Status May 214 see Nepomuk s talk > VERITAS started full operations in 27 2 and 3-telescope operations before this date > several major upgrades in the past years boost in sensitivity >3% (T1 move) lower energy threshold: <1 GeV (camera and trigger upgrade) better calibration - improved systematics (e.g. mirror alignment or flasher calibration) > data archive of >6 hours > very stable operations (~95%) no known critical hardware issues which would prevent us from operating >5 years > stable operational funding for the next years (DOE, NSF, SAO) LTP & Performance May 214 4
Require 5σ and >1 events per energy bin Sensitivity after Funk et al (CTA, 212) and Abeysekara et al 213 VERITAS 1 hrs 4 bins per decade energy (equal bin size on log scale) LAT - 5 yrs HAWC-1 1 yr CTA - 1 hrs HAWC 1 yr/5yrs Crab x.1 CTA - 1 hrs LTP & Performance May 214 5 LAT(?)/HAWC: 24/7 duty cycle; IACTs
Detection Sensitivity 3σ is (of course) only an indication observation time [h] 3 1 2 1 1 1 5σ 3σ >1 events >1 events.5% - 1 h 1% - 25 h 5% - 1.5 h 1% -.5 h -1 1-3 1-2 1-1 1 flux [Crab Units] LTP & Performance May 214 6
Future upgrades. analysis improvements observation time [h] 3 1 2 1 1 1 3σ is (of course) only an indication 5σ 3σ >1 events >1 events.5% - 1 h 1% - 25 h 5% - 1.5 h 1% -.5 h > VERITAS standard analysis based still based on image parameters > two new analysis methods almost methods almost ready for science use: MVA based (boosted decision trees) image template method > Significant improvements seen: 1% Crab in <2h -1 1-3 1-2 1-1 1 flux [Crab Units] LTP & Performance May 214 7
Moonlight observations > new observation modes for increased temporal coverage ~85 hours of normal operations ~2 hours of moonlight operations (at nominal + reduced HV) ~25 hours of bright moonlight observations with UV filters in front of the cameras Optical Filter properties J.Holder LTP & Performance May 214 8
Effective areas - example ] 2 effective area [m 6 1 5 1 1 4 3 1 2 1 Camera upgrade normal operation reduced HV UV filter pre-upgrade normal operation Preliminary 1 1-1 1 1 1 energy [TeV] LTP & Performance May 214 9
Angular and energy resolution angular resolution [deg].35.3.25.2.15 Fermi LAT VERITAS HAWC Tycho 8 diameter.1 68%.5 containment radius 1-2 -1 1 1 1 energy [TeV] LTP & Performance May 214 1 Abeysekara et al 213 LAT Performance page
LTP & Performance May 214 11
Large zenith angles 3-4% improvement in sensitivity for large zenith angle observations Crab Nebula observations at >55 deg VERITAS (214) Allows high-precision mapping of the inner Galaxy at energies >5 TeV LTP & Performance May 214 12
Pointing and systematic errors > pointing of each telescope is continuously monitored > systematic error on pointing less than 5 1 LTP & Performance May 214 13
Energy reconstruction E.3 energy resolution.25.2.15 Fermi LAT VERITAS important for high-statistic studies of spectral cut offs.1.5 1-2 -1 1 1 1 energy [TeV] (note: strong dependence on quality cuts) LTP & Performance May 214 14
Systematic uncertainties in energy reconstruction > main sources for systematic uncertainties atmosphere calibration Monte Carlo simulations analysis > intensive work on improved calibration many values are measured now independently with different methods > as all systematic errors, extremely hard to estimate > assumed to be less than 2% on energy atmospheric profiles translation into flux uncertainty depends on spectral index, typically between 2 and 4% LTP & Performance May 214 15
Observational constrains observing hours / day 12 1 8 6 Moon Monsoon VERITAS 21 4 2 552 5525 553 5535 554 5545 555 5555 MJD LTP & Performance May 214 16
Observing the Galaxy with VERITAS Dots are known TeV sources LTP & Performance May 214 17 Assuming elevations>5
Observing the Galaxy with VERITAS Dots are known TeV sources LTP & Performance May 214 18 Assuming elevations>3deg
5 5 4 June 8 7 5 6 8 7 5 6 1 5 March -1 July 8 7 5 6 3 3 April 7 5 6 5 4 1 5-1 August 2 7 6 5-1 -1-1 8 7 5 6 5 4 3 2-5 1 1-1 December 8 7 5 6 5 4 3 3 2-5 1 1 1 4 2-5 1 Gernot Maier 1 LTP & Performance May 214 November 8 3-5 2 1 8 4 1 2-5 -1 5 1 5 4 6-5 1 1 7 5 4 2-5 8 1 3 2-5 -1-1 October 4 1 3 2 1 1 5 3-5 6-1 7 5 8 1 1 February 2-5 1-1 4 3 2-5 5 4 1 1 6 3 2-5 7 5 8 6 7 5 September 1-1 Assuming elevations>3deg 4 8 5 May 6 7 5 8 3 Average elevation January
Summary > VERITAS is a mature VHE instrument with well understood performance and systematic errors > The coming 5 years will provide unprecedented wide-band coverage of the gamma-ray sky, along with complementary multi-messenger facilities > Galactic long-term plan discussions today: SNRs, PWN, Pulsars, Binaries, Surveys and discoveries LTP & Performance May 214 2