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Wide Field of View surveying in Next Generation GeV/TeV Observatories. D. Kieda University of Utah. Milagro Cygnus Arm Detection. Significance is 5.5 (Crab is 5.9) Source extent is ~5 o Implied source flux is several Crab. - PowerPoint PPT Presentation
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October 21, 2005UCLA Gamma Ray Workshop
Wide Field of View surveying in Next Generation GeV/TeV
Observatories
D. KiedaUniversity of Utah
October 21, 2005UCLA Gamma Ray Workshop
Milagro Cygnus Arm Detection
R. Atkins et al, 22nd Texas Symposium on Astrophysics, Stanford (2004)
•Significance is 5.5 (Crab is 5.9)•Source extent is ~5o
•Implied source flux is several Crab
October 21, 2005UCLA Gamma Ray Workshop
Whipple Follow-up
● No Strong point source evident (given # of trials)●Typical point source flux limit~300 mCrab ● Quoted for E > 400 GeV , angular resolution ~ 0.05o.●Milagro source diameter >> f.o.v. of Whipple camera
G. Walker, Ph.D Thesis, U of Utah (2004)
October 21, 2005UCLA Gamma Ray Workshop
Source Detectability
source resolution
Source Size < Angular resolution
= Point Sources: CrabAGNM87
KA
A
FF
TA
A
FF
TNS
peff
eff
resolutioncrpeff
eff
resolutioncr
141
),,,,,( crresolutionpeffeff FAATKfF
constant
October 21, 2005UCLA Gamma Ray Workshop
Source Detectability
source resolution
'14
1 KA
AFF
TA
AFF
TNS
peff
eff
sourcecrpeff
eff
sourcecr
Source Size > Angular Resolution
= Diffuse Sources: SNRTibet-Milagro UIDMolecular Cloud
sourceF
n.b. if Source has internal structure you will do better 1;' KNS
October 21, 2005UCLA Gamma Ray Workshop
HESS Diffuse Sources
Many sources appear to have internal structure:
Ability to resolve a diffuse source is a key to determining its astrophysical processes
(HESS , 2005)
October 21, 2005UCLA Gamma Ray Workshop
Source Resolvability
source resolution
Source Size > Angular Resolution
Just need some factor >1 more S/Nto resolve internal source structure
KA
AFF
TA
AFF
TNS
peff
eff
sourcecrpeff
eff
sourcecr
14
1
sourceF
October 21, 2005UCLA Gamma Ray Workshop
Source Resolvability
resolution
Source Size < Angular resolution
As F increases, tails of Gaussian become detectable->resolve source size
resolutiond
source resolution
F
K
22
2
2121
source
resolution
r
sourcepeff
effeff
sourcecr
erdrA
A
FF
TK
2
2
2)( source
resolution
eKgF source
October 21, 2005UCLA Gamma Ray Workshop
Source Detect/Resolve
Detected(both)
DetectedMilagro only
Whipple
Increased Milagro sensitivityfor extended source
•longer exposure•Wider fov
Excellent Point Source sensitivity of IACT does not help here
Note that this plot neglects energy threshold benefits of IACTs
X
October 21, 2005UCLA Gamma Ray Workshop
Newer Arrays
Extended Sources:Molecular cloudsSNRPoint Sources:AGNPulsar
Diffuse Sources:Galactic PlaneGalactic Arm
Next Gen is 1 km2 IACT, 5 deg f.o.v, 1 mCrab/50 hours
October 21, 2005UCLA Gamma Ray Workshop
Larger SourcesImaging Source diameters > IACT f.o.v requires multiple pointing
4 pointings: 200 hours: about the most one can do per year
Larger areas require reduced time/pointing, thereby reducing sensitivity
Intersect at(Fx, x)
HF0NF0
October 21, 2005UCLA Gamma Ray Workshop
Larger Sources vs. Wider f.o.v IACTs
NfovH
resolution
Nresolution
N
H
x FF
0
0
NfovN
Nresolution
Hresolution
H
x FFF
0
2
0
H=HawkN=Next Gen
Typical
Nfovx 5.2
Nfovx millCrabF )/(125
October 21, 2005UCLA Gamma Ray Workshop
Source sensitivity depends on source diameter
If Cyg Arm is truly diffuse source, it is barely accessible to current IACTNext Gen area 100 x HAWC can compensate for 10% on-time efficiency
Next Gen ( 1 km2) IACT superior forNext Gen needs fov > 100 in order to resolve 250 diffuse sources Next Gen better for resolving sources, point sources, looking deeperHAWC-type better for large diffuse sources (ignoring energy threshold differences)
Summary
fovsource 5.2
October 21, 2005UCLA Gamma Ray Workshop
HAWC All-sky: Monitor + large scale structureLarge IACT Next Gen looks deep, low E (followup), spectral/time evolutionLimited energy range above 10 TeV-200 TeV: probe with km2 array of small (1 m class) dedicated imagers
Strategy
Study/design phase: Next year?Pursue Modular design:
• quick test/low cost•allow deploy/test subsystem at high altitude?•Site testing?•Easy final deployment, cheaper fabrication/maintenence