VERITAS: Very Energetic
Radiation Imaging Telescope
Array System
Frank Krennrich
Iowa State University, Ames, IA
Gamma 2003, Adler Planetarium
24 April, 2003
Collaboration Members:
Iowa State U.
Leeds U. (U.K.)
McGill U. (CA)
Purdue U.
Smithsonian Astrophysical Observatory
UCLA
University College, Dublin (Ireland)
U. of Chicago
U. of Utah
Washington U.
Gamma 2003, Adler Planetarium
24 April, 2003
Outline
• Science Goals of VERITAS
• VERITAS Instrument
• Status Report
• VERITAS Capabilities
Gamma 2003, Adler Planetarium
24 April, 2003
Science Goals: General
VERITAS will provide:
1. Excellent sensitivity – VHE source studies – more sources, more
detailed spatial/spectral studies, discovery potential for the unexpected.
2. Versatility – telescope array will provide a range of capabilities: greatest
sensitivity and lowest energy threshold, wide angle surveys and multiple
source observing.
3. Wide range of science goals – detailed astrophysics of known sources
and very exciting, speculative new ideas. For many objects, we will
move from population studies to detailed astrophysical studies.
4. Strong Connections to other HE, VHE, UHE, neutrino studies.
Gamma 2003, Adler Planetarium
24 April, 2003
Overview of VERITAS Science
Active Galactic Nuclei *
Extragalactic Background Light
Gamma Ray Bursts
Shell-type Supernova Remnants
Galactic Diffuse Emission
Gamma-ray Pulsars
Plerions
Unidentified Galactic EGRET Sources
Dark Matter (Neutralino Annihilation)
Cosmic Ray Origin
Lorentz symmetry violation
Primordial Black Holes
Gamma 2003, Adler Planetarium
24 April, 2003
VERITAS Science: AGNs, EBL
• Active Galactic Nuclei
• Infrared Background
g + g  e+ + e -
from Hauser & Dwek, ARA&A, 39, 249 (2001)
6 min @ 4.5 Crab
27 min
@ 2.8 Crab
6 min @ 1.2 Crab
Krennrich, F. et al. 2002, ApJL, 575, L9
Gaidos, JA.. et al. 1996, Nature, 383, 319
Gamma 2003, Adler Planetarium
24 April, 2003
Multiwavelength Observations:
Mrk 501 Spectral Energy Distribution (SED)
Correlation in
variability between
synchrotron and g-ray
emission naturally
explained by IC:

Same population of
electrons produce both
components.
g-Ray measurements
provide separate
constraint on electron
energy, breaks
degeneracies.
Gamma 2003, Adler Planetarium
24 April, 2003
Variable Sources
• Multiple facilities separated by longitude to reduce day-night
data gaps for multiwavelength monitoring
VERITAS,
2003 1 tel.
2005 4 tel.
2007 7 tel.
HESS, 4 tel., 2004
Gamma 2003, Adler Planetarium
MAGIC, 1 tel.,
2003+
CANGAROO III, 4 tel., 2005
24 April, 2003
VERITAS-4/VERITAS-7: Concept
- Montosa Canyon
- Dark site, well shielded by
surrounding hills
- 1km of the FLWO Basecamp
Gamma 2003, Adler Planetarium
24 April, 2003
VERITAS-4/VERITAS-7: Concept
VERITAS Philosophy:
- Improve Flux Sensitivity
- Reduce Epeak
- Array of “12 m” telescopes
- Imaging Cameras
- Improved Optics
- Improved Camera
- Flexible Operation using
Subarrays
- Efficient Operation (well
developed location)
- New Technology where
appropriate.
Gamma 2003, Adler Planetarium
24 April, 2003
Array Layout, Specifications
Reflector:
Diameter – 12m
F/number – 1.0
Number of facets – 350
Facet size – 61 cm
Ground-glas mirrors
Telescope Camera:
Number of Pixels - 499
Pixel size - 0.15 deg
Field of View - 3.5 deg
L=80m
F=12m
Array:
Three telescopes spaced
equidistantly on the circle of 80 m
radius and one telescope in the
center  V7 add 3 more telescope
Electronics:
D=12m
Gamma 2003, Adler Planetarium
Fast pre-amp/cables
500 MHz FADC
Real time array trigger,
flexible trigger (ms bursts)
24 April, 2003
Prototype Telescope
• Purpose – verification of all VERITAS technical designs.
•
•
•
•
•
Become the first VERITAS telescope.
Site near Whipple “base camp” – first telescope ultimately
moved to VERITAS site
Approximately one half of the camera pixels to be
installed, ~250 channels
Half of the mirror segments installed
Full telescope drive and OSS
Prototype observation facility and electronics in trailer onsite
Gamma 2003, Adler Planetarium
24 April, 2003
Positioner & Reflector
- 12m reflector (350 mirrors).
- Commercial positioner
(delivery early May 2003)
Gamma 2003, Adler Planetarium
24 April, 2003
Positioner Construction
- positioner parts at RPM-PSI.
- delivery to site early May 2003
Gamma 2003, Adler Planetarium
24 April, 2003
Optical Support Structure
- Design exceeds specifications –
decentering and blur
(delivery mid May 2003)
Gamma 2003, Adler Planetarium
24 April, 2003
Optical Support Structure
- OSS assembly in Chandler (near Phoenix AZ)
- installation at site May 2003
Gamma 2003, Adler Planetarium
24 April, 2003
OSS design results
Specifications:
Decentering < 0.02 degree
Blur < 0.02 degree
Bias Alignment
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24 April, 2003
Mirrors
Radius <R> = 23.92 m +/- 0.4%
Measuring Set-up
Blur
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<D> = 4.9 +/- 1.9 mm
24 April, 2003
Camera Components
Measured Pulse Response
(preamp+30m high
bandwidth cable)
Gamma 2003, Adler Planetarium
24 April, 2003
Trigger Rates
NSB Flux:
0.11 pe deg-2 m-2 nsec-1
Telescope Trigger:
3 adjacent pixels above
operation threshold
Array Trigger:
3 out of 4 telescopes
Threshold: 5.6 pe
Expected CR Rate:
~200 Hz
Gamma 2003, Adler Planetarium
24 April, 2003
Electronic Components
Fast Pre-Amps (ISU)
High Bandwidth
cables (Utah)
CFDs (Utah)
L2 Trigger (Leeds)
CMB (ISU)
FADC boards
(Wash. U.)
HV (Chicago)
Inside Camera
Electronics Shed
Gamma 2003, Adler Planetarium
24 April, 2003
Noise Level:
Gain match with anode current
System (PMT/preamp/cable) noise level
into FADC. Here, 1 p.e.~2mV at
operating gain.
rms noise (microV)
600
500
400
300
200
100
0
0
5
10
15
20
25
30
35
channel number
Gamma 2003, Adler Planetarium
24 April, 2003
Cherenkov Events
3-fold event trigger: Cherenkov event
display (software: Wash. U.)
Large Event - gain switch
Getting >10bits from an 8bit FADC chip
by signal delay switch (Cherenkov pulse)
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24 April, 2003
Camera
Half the camera stuffed (250 pixels)
Gamma 2003, Adler Planetarium
24 April, 2003
Camera Integration
In progress in Chicago high-bay area
Light-tight building for camera
Camera and light-flasher
Gamma 2003, Adler Planetarium
Electronics Trailer
24 April, 2003
Improvement in Sensitivity
Combine stereoscopic view with improved
12m telescope
• improved angular resolution
• enhanced background suppression
• lower energy threshold
• improved energy resolution
VERITAS-7
80 m
Gamma 2003, Adler Planetarium
- 50 GeV – 50 TeV
- Dq/q ~ 0.03o @1TeV
~ 0.09o @100GeV
- Flux sensitivity:
15 mCrab @100GeV
5 mCrab @300GeV
- DE/E ~ 0.1 - 0.15
24 April, 2003
Improvement in Sensitivity
Analysis
parameters:
Exposure:
50 hours
Spectrum resolution:
DN/N= 0.2
Whipple 10m
Telescope
VERITAS
4 Telescope
Array
Gamma 2003, Adler Planetarium
24 April, 2003
Sensitivity (Deep Observations)
Exposure:
50 hours
Crab Nebula
Required spectrum
resolution: 20%
(equivalent to 5s above
background or > 25 photons
in each energy bin).
1H1426+428
Z=0.129
In low state
“1H1426+428”
at Z=0.25
Gamma 2003, Adler Planetarium
Array Energy
resolution:
DE/E ~ 0.15 – 0.10
Conservative Sensitivity
based on measuring
spectra (not discovery).
24 April, 2003
Differential g-ray Rates
Crab Nebula
VERITAS-4
35 photons per min
VERITAS-7
50 photons per min
Substantial
sensitivity
below Epeak.
Gamma 2003, Adler Planetarium
24 April, 2003
Summary
• First light of VERITAS Prototype in September 2003
• VERITAS-4 will be a very powerful and world-class
instrument coming online in 2005.
• VERITAS-7  2007
• VERITAS strongly complements GLAST, ICECUBE,
AUGER and other missions in HE & particle
astrophysics
Gamma 2003, Adler Planetarium
24 April, 2003
Appendix: g-ray Detection rates
Crab photons
Exposure:
50 hours
Required spectrum
resolution:
CR hadrons
CR electrons
20%
(equivalent to 5s above
background or > 25 photons
in each energy bin).
Angular resolution:
(1s of 2d Gaussian w/in
angular acceptance)
100 GeV - 7.5 arc min
1 TeV - 4.3 arc min
10 TeV - 1.6 arc min
Gamma 2003, Adler Planetarium
24 April, 2003
Appendix: VERITAS-4, VERITAS-7
VERITAS-4
VERITAS-7
Peak Energy
110 GeV
90 GeV*
Crab Nebula
Detection Rate
35 photons per minute
50 photons per minute
Collecting Area
10 TeV
1 TeV
100 GeV
3x109 cm2
2.2x109 cm2
3.3x108 cm2
+ 20%
+ 20%
+ 90%
Flux sensitivity (50h)
10 TeV
1 TeV
100 GeV
3.7x10-12 erg cm-2 s-1
1.4x10-12 erg cm-2 s-1
1.4x10-11 erg cm-2 s-1
Sky survey operation
Single exposure
*
3% lower
10% lower
30% lower*
Double exposure
potential for combining mirror area during analysis has not been fully exploited
Gamma 2003, Adler Planetarium
24 April, 2003
Next-generation VHE Telescopes
GLAST (2006)
VERITAS-4 (2005)
MAGIC (2003)
HESS (2004)
CANGAROO (2005)
AM-2 / ICECUBE
• Good global coverage - latitude & longitude. Required by science.
• VERITAS & MAGIC observe same sources as IceCube.
• GLAST launch: worldwide VHE network – timing is good!
Gamma 2003, Adler Planetarium
24 April, 2003
VERITAS Multiwavelength
VERITAS has strong contacts to other wavelengths
(SAO is largest multi-wavelength astronomy unit).
Actions:
• Point of Contact established (Lucy Fortson).
• Sponsorship of meetings (upcoming April 25-27, 2003).
• VERITAS observing plan will be available on WWW site.
• Guest observing possible through Associates Program.
• Fast (< 1 day) electronic publication of quick-look data.
Gamma 2003, Adler Planetarium
24 April, 2003
Astronomical Perspective
VERITAS will have broad astronomical impact. Examples:
• X-ray studies of blazars, GRB’s (EXIST, SWIFT).
• Imaging studies of SNR’s, origin of pulsed radiation.
• Measuring the EBL (Optical/IR) – cosmology.
• ...
SOURCES
GLAST
VERITAS
Gamma 2003, Adler Planetarium
24 April, 2003