VERITAS The choice of the next generation

1
VERITAS The choice of the next generation
Jojo Boyle
Britney
2
GAMMA-RAY ASTRONOMYS GREAT FAILURE
Although GeV-TeV gamma-ray astronomy gas had a
number of outstanding successes, (the detection
of blazars, the GeV component in solar flares,
the GeV-TeV component of GRBs, pulsars, shell and
plerionic supernova remnants, the galactic plane,
to name but a few), the single great motivator,
the conclusive solution to the problem of the
origin of cosmic radiation, is still elusive.
It was this problem more than any other that led
to the development of high energy gamma-ray
astronomy, both in space and on the ground, but
in some ways, at least observationally, we are no
closer to identifying the source than we were 40
years ago.
While we can celebrate the contributions of
gamma-ray studies to pulsar phenomenology, to
limiting the infrared background, to the study of
jets in extragalactic sources, we cannot proclaim
with any confidence Gamma-ray astronomers find
the Origin of the Cosmic Radiation T.C.
Weekes, 2000
3
Talk outline
Part 1 Introduction to the development of Imaging
Atmospheric Cerenkov Technique and a summary of
important results Part 2 Why do we need more
than one telescope ? Status of development of the
VERITAS system.

• If you want to sleep now, you can read more at
• Weekes et al., Astroparticle Physics 17 (2002)
  221-243
• http//veritas.sao.arizona.edu

4
Part 1

• Blood, sweat and tears
• The opening of a new window of Astronomy

5
Photo J. Kildea
6
How we detect Gamma-rays
7
1 Pixel 1968-1976 1o fov, 1o trigger
37 Pixels 1982-1987 3.5o fov, 2.4o trigger
109 Pixels 1987-1996 3.0o fov, 2.6o trigger
151 Pixels 1996-1997 3.3o fov, 2.6o trigger
331 Pixels 1997-1999 4.8o fov, 4.8o trigger
490 Pixels 1999-Present 3.8o fov, 2.6o trigger
8
First Generation (1968 1976)
Crab 5s in 5 years
1 Pixel 1o fov 1o trigger
Crab Detection (Fazio 1972)
Atmospheric Cerenkov Imaging proposed by Weekes
Turver, 1977
France wins Eurovision Song Contest
9
Gamma-Hadron seperation
300 GeV g-ray
Hillas Parameters (A. M. Hillas, University of
Leeds, UK)
1 TeV proton
Led to development of 2nd Generation Cerenkov
Telescopes
10
First Imaging Camera(1982 1987)
Crab at 5s in 50 hours
37 Pixels 3.5o fov, 2.4o trigger
Crab Detection (Weekes 1989)
More astrophysicists than photons
VERITAS concept first described by Weekes (1985)
11
Success at Last(1987 1996)
109 Pixels 3.0o fov, 2.6o trigger
Crab at 5s lt 2 Hours
1st TeV Energy Spectrum Crab Nebula (Mohanty,
1996)
Extragalactic Detections Markarian 421 (Punch,
1992)
Markarian 501 (Quinn, 1995)
1es 2344 (Catanese, 1996)

Extreme variability observed in Markarian 421
(First flare 1994)
12
Markarian 421 (1996)
Gaidos et al, Nature 383 (1996) 319

• Gave us an insight into
• the size of the emission region
• Doppler Boost Factor (beamed)
• Bulk Lorentz Factor
• Quantum Gravity

Eqg 4 x 1016 GeV
(Planck Mass 1019 GeV)
13
Success at Last(1987 1996)
109 Pixels 3.0o fov, 2.6o trigger
Crab at 5s lt 2 Hours
1st TeV Energy Spectrum Crab Nebula (Vacanti,
1991)
Extragalactic Detections Markarian 421 (Punch,
1992)
Markarian 501 (Quinn, 1995)
1es 2344 (Catanese, 1996)

Extreme variability observed in Markarian 421
(First flare 1994)
ARTEMIS (Antimatter Research Through the Earth
Moon Ion Spectrometer) First Run 1993/4, Second
Run 1996 (Pomarede and Boyle, 2000)
14
Is bigger better I ?(1996 1997)
151 Pixels 3.3o fov, 2.6o trigger
Crab at 5s in 1.5 Hour
Search for Pulsed Emission
15
Pulsed Emission Results
g-rays are attenuated by pair production in
intense magnetic fields near pulsars Polar Cap
Model predicts a super exponential cut
off. Outer gap model does not predict such sharp
cut off.
As of yet, no evidence of pulsed emission at very
high energies.
16
Is bigger better I ?(1996 1997)
151 Pixels 3.3o fov, 2.6o trigger
Crab at 5s in 1.5 Hour
Search for Pulsed Emission
Extensive Supernova Survey Galactic Plane
Searched Gamma-Ray Burst Alert Optimized
17
Is bigger better II ?(1997 1999)
331 Pixels 4.8o fov, 4.8o trigger
Crab at 5s in 1.0 Hour
Introduction of Pattern Selection
Trigger (University of Leeds, UK)
Established AGN monitored EGRET Unidentified
Searches Supernova Survey
18
Supernova Results
Observations above 100 MeV by the EGRET
instrument have found gamma-ray signals
associated with at least three SNRs IC 443 and
gamma-Gygni and the Monoceros SNR - Rosette
Nebula region. Interpreted as evidence for
cosmic ray acceleration using the model of Drury,
Aharonian and Volk (1994)

• IC443
• gamma-Cygni
• W44,
• W51
• W63
• Tycho
• Cassopeia A
• Monoceros SNRRosette Nebula

( Buckley et al., AA, 329, 639 )
19
Lets get closer(1999 Present)
Crab at 5s in ½ Hour
490 Pixels 3.8o fov, 2.6o trigger
Pattern Selection Trigger Constant Fraction
Discriminators
VERTIAS electronics tested
Science mainly AGN focused
Detection of H1426 (Horan, 2000) at z 0.129
Confirmation of 1es1959 (May 2002) at z 0.048
20
Infrared Background
Whipple Results, 1998
from Primack et al., Astroparticle Physics,
(1999), 11, 93
From Biller et al., (1998) Phys. Rev. Lett., 80,
2992
21
Part 2

• Why we need more telescopes

Duty cycle of Cerenkov Telescope is only 7
(Clear Moonless nights)
Current analysis methods reject 99.7 of the
background but only retain 60 of the gamma-rays
Dominant background is from muons falling far
away from the optic axis
22
Stereo view of a g-ray showers
Unique view of showers Reduce your background to
zero Can operate at low threshold (all
telescopes) or in singular mode for greater
coverage of objects
23
VERITAS Collaboration
Iowa State University Lewis, Krennrich,
LeBohec Smithsonian Astrophysical
Observatory Weekes, Gibbs, Criswell,
Horan National University of Ireland Quinn,
Fegan, Lang, Gillanders, Moriarty Leeds
University, UK Rose, Knapp, Holder,
Hillas DePauw University, Indiana Kertzman
Purdue University Finley, Cu, Falcone,
Gaidos University of California, Los
Angeles Ong, Zweerink University of Chicago
Swordy, Muller, Wakely, Boyle,
Fortson University of Utah Keida,
Vassiliev University of Washington, St.
Louis Buckley, Krawjinski,
24
VERITAS 499 Pixels 3.5o fov 3.5o Tigger
Crab at 5s lt 1 minute
25
Sensitivity
VERITAS-4
- 100 GeV 50 TeV - Dq/q 0.04o _at_1TeV
0.12o _at_100GeV - Flux sensitivity
200 mCrab _at_100GeV 6 mCrab _at_300GeV
VERITAS-7

• - 50 GeV 50 TeV
• - Dq/q 0.03o _at_1TeV
• 0.09o _at_100GeV
• - Flux sensitivity
• 15 mCrab _at_100GeV
• 5 mCrab _at_300GeV

Telescope based on existing Whipple 10m. Focal
length to be increased to 12m
26
SAO Whipple Ridge Site
10m Reflector
Photo John Kildea
27
SAO Whipple Ridge Site
2Mass
10m Reflector
48 inch
60 inch
Photo Steve Fegan
28
Proposed VERITAS Site
SAO Basecamp
Ridge 15km
Elevation 1400 m
29
30 channel test (Dec 2001)

• Purpose to verify designs and specification
  targets for the front-end electronics
• 30 channels of VERITAS electronics from
  photomultipliers through FADC output tested at
  Whipple observatory.
• PMTs mounted in a small cluster on focus box,
  cable lengths of 130 (similar to VERITAS) are
  used.
• Major test objectives
• Pulse bandwidth of system
• Noise of system
• Operation of FADCs
• Operation of CFDs

30 VERITAS pmts in Whipple focus box (Purdue,
Iowa)
30
Electronic Components
30 x Constant Frac. Discriminators (Utah)
3 x 10 channel FADC boards (Wash. U.)
High Bandwidth cables (Utah)
30 ch. HV and preamp system and power (Iowa,
Chicago)
31
Measured Pulse Response (preamp30m high
bandwidth cable)
Camera Components
32
Cherenkov Events
Large Event - with gain switch pulse
3-fold event trigger Cherenkov event display
(software Wash. U.)
33

• 30 Channel Tests Results
• Bandwidth specs OK
• pmt/preamp/cable noise specs OK
• FADC system functional
• CFD/FADC combination OK
• HV system OK
• preamp/anode current monitor system OK

STATUS Development stops this week Electronic
component production starts next week Camera
Integration in Chicago October 2002 Integration
on site for 250 channel prototype, January
2003 First Light in early 2003 Four telescopes
online 2006
34
New Ground Based Experiments
35
Conclusions

• Whipple telescope continues to produce great
  science.
• VERITAS technical developments are going well
  and on-schedule.
• Plan developed to provide an initial 4 telescope
  array at the VERITAS site, operational by 2006.
• Exciting results for Erice 2006

36
Galactic Astrophysics

• Shell-type supernova remnants and cosmic rays
• Compact Galactic Objects

37
Supernova Remnants

• SNRs widely believed to be the sources of cosmic
  rays up to Z x 1014 eV.
• 20 Shell-type SNRs with known distances lie
  within 4 kpc.

38
Cosmic Ray Composition
Elemental composition not well known above 1
TeV Supernova acceleration limit at Z x 1014
eV (Cesarky )
39
Compact Galactic Objects

• Pulsar-powered Nebulae
• Gamma-ray Pulsars
• Unidentified galactic EGRET sources
• Galactic plane survey

40
Pulsar-powered objects

• Able to detect Crab Nebula like objects anywhere
  within the galaxy (dec gt -28o)

41
Current Status of Pulsar Observations
No evidence of pulsed emission at very high
energies.
42
Egret Unidentified Sources
Over 170 unidentified sources detected
43
Galactic Plane Survey
EGRET all sky map
44
Starburst Galaxies

• Higher star formation rate, therefore higher rate
  of supernova.
• May detect gamma-rays from po decay

45
Gamma Ray Bursts
46
Interstellar Infrared Background
47
Physics

• Neutralino Annihilation in the Galactic Center
• Quantum Gravity
• Primordial Black Holes

48
Neutralino annihilation

• Mass range in the order of
• 30 GeV lt c lt 3 TeV
• VERITAS can search indirectly for WIMPs by
  looking for gamma-rays from annihilation of
  WIMPs in the Galactic Center.

Why the Galactic Center ? 1. Location and
Magnetic Field around central massive blackhole
may enhance the emission significantly 2.
Annihilation process is proportional to the
square of the neutralino density, dark matter
halo peaks in the Galactic Halo.
49
Quantum Gravity
Planck Mass 1019 GeV
Eqg 4 x 1016 GeV
50
Primordial Black Holes

• Emit burst of Radiation in their final stages of
  evaporation.
• Standard model 1030 erg in 1 sec with energy
  peaked near 1 TeV
• 2 years of observations could reach sensitivity
  level of evaporation of
• 700 pc-3yr-1