Water Cherenkov Technology in Gamma-Ray Astronomy Gus Sinnis Los Alamos National Laboratory.
-
Upload
stuart-garrison -
Category
Documents
-
view
214 -
download
0
Transcript of Water Cherenkov Technology in Gamma-Ray Astronomy Gus Sinnis Los Alamos National Laboratory.
Complementarity of Gamma-Ray Detectors Large Aperture/High Duty CycleMilagro, Tibet, ARGO, HAWC
Large Area
Good Background Rejection
Large Duty Cycle/Aperture
Sky Survey
Extended Sources
Transients (AGN, GRB)
Highest Energies
Galactic Diffuse Emission
Low Energy ThresholdEGRET/GLAST
Space-based (Small Area)
“Background Free”
Large Duty Cycle/Aperture
Sky Survey
AGN Physics
Transients (GRBs)
High SensitivityHESS, MAGIC, VERITAS
Large Area
Excellent Background Rejection
Low Duty Cycle/Small Aperture
High Resolution Spectra
Study of known sources
Limited Surveys
Fast Flaring
Distant AGN
Goals of a TeV Gamma-Ray Survey Instrument
• Galactic cosmic-ray origins– Galactic diffuse emission– Highest energies (>10 - 100 TeV)
• Particle acceleration in astrophysical jets– Gamma-ray bursts– Active galaxy transients– Multi-wavelength/messenger campaigns
• All-sky survey– Discovery potential– IACT alert system
Galactic Cosmic Rays
• Measure Galactic accelerators to >100 TeV• Measure diffuse emission spatial and spectrally
resolved– Large area (100,000 m2)– High duty factor (~100%)– Large field-of-view (~2 sr)
EGRET
Milagro
pion channel
Inverse Compton
channel
EGRET all sky (100 MeV)
Strong & Moskalenko
Cygnus Region
• Absorption by EBL requires– Low energy threshold– 200 GeV for z = 0.5 horizon– 1-2 TeV for z = 0.1 horizon
Extragalactic transients
Fermi/LATScienceExpress 2/19/2009
GBMLA
T
• Gamma-Ray Bursts– GeV ≥ 0.1 x MeV fluence– 10-7 ergs/cm2 @ 10 sec– 4000 m2 @ 200 GeV
GeV = 0.1 100keVGeV = 100ke
V
MAGIC collab.
Extensive Air Shower Arrays
http://www.ast.leeds.ac.uk/~fs/photon-showers.html
4 km
1 TeV
gamm
a-ray shower Longitudinal P
rofile
7.7 km
30 km
meters
• gammas• electrons
gamma:electron ratio ~6:1em particles sparse at low energiesneed enclosed area ~ active detector area 200 m
Tibet AS
Active detectors
Milagro
Background rejection in EAS arrays
’s within a 105 m2 area of core
Large fluctuations of shower size manifest as fluctuations
in muon content
Milagro – 1st Generation
8 meters
e
80 meters
50 meters
• 2600m asl
• 898 detectors
– 450(t)/273(b) in pond
– 175 water tanks
• 4000 m2 (pond) / 4.0x104 m2 (phys. area)
• 5-40 TeV median energy (analysis dependent)
• 1700 Hz trigger rate
• 400 Gbyte/day
• 0.3o-1.2o resolution (0.75o average)
• 95% background rejection (at 50% gamma eff.)
Background Rejection in MilagroProton MC Proton MC
Data Data MC MC
Hadronic showers contain penetrating component: ’s & hadrons
– Cosmic-ray showers lead to clumpier bottom layer hit distributions– Gamma-ray showers give smooth hit distributions
Background Rejection (Cont’d)
( )mxPE
nFitfOut+fTop=A
∗4
mxPE: maximum # PEs in bottom layer PMT
fTop: fraction of hit PMTs in Top layer
fOut: fraction of hit PMTs in Outriggers
nFit: # PMTs used in the angle reconstruction
Apply a cut on A4 to reject hadrons:A4 > 3 rejects 99% of Hadrons
retains 18% of Gammas
S/B increases with increasing A4
Background Rejection ParameterBackground Rejection Parameter
TeV Observations of Fermi Sources
• 34 Fermi BSL Galactic sources above declination of -5o
• 14 detected by Milagro above 3– FDR Miller 2001 estimates 1% false positive rate
• 5 new TeV sources
• Geminga 6.3 as extended source (2.6o fwhm)
Boomerang Cygnus Region
MGRO 1908+06HESS 1908+063
Geminga
Crab Nebula
Fermi Sources
GemingaPulsar
Milagro C3
Pulsar (AGILE/Fermi)
MGRO 2019+37
Fermi PulsarCygni SNR Fermi Pulsar
HESS 2032+41MGRO 2031+41
MAGIC 2032+4130
Fermi PulsarMilagro (C4)
3EG 2227+6122Boomerang PWN
IC433SNR
MAGICVERITAS
Radio pulsar J0631+10
(new TeV source)unID
(new TeV source)
unID(new TeV source)
Fermi PulsarMGRO 1908+06HESS 1908+063
W51HESS J1923+141
SNR
G65.1+0.6 (SNR)Fermi Pulsar (J1958)
New TeV sources
HAWC: The Next Generation
The base of volcán Sierra Negra• latitude : 18º 59’• longitude: 97º 18’• altitude : 4100mInside Parque Nacional Pico de Orizaba2 hours from Puebla (INAOE)
15x Milagro sensitivity 5x larger active detector area optical isolation of detector elements10x larger muon detector improved angular resolution improved energy resolution higher altitude (4100 m)1/3 median energy of Milagro
The HAWC Collaboration
Los Alamos National LaboratoryB. Dingus, J. Pretz, G. Sinnis
University of MarylandD. Berley, R. Ellsworth, J. Goodman, A.
Smith, G. Sullivan, V.Vasileiou
University of New MexicoJ. Matthews
University of UtahD. Kieda
Michigan State UniversityJ. Linnemann
Pennsylvania State UniversityTy DeYoung
NASA/GoddardJ. McEnery
Naval Research LabA. Abdo
UC Santa CruzM. Schneider
Instituto Nacional de Astrofísica Óptica y Electrónica
Alberto Carramiñana, L. Carasco, E. Mendoza,S. Silich, G. T. Tagle,
Universidad Nacional Autónoma de MéxicoR. Alfaro, E. Belmont, M. Carrillo, M. González, A. Lara,
Lukas Nellin, D. Page, V. A. Reese, A. Sandoval, G. Medina Tanco,O. Valenzuela, W. Lee
Benemérita Universidad Autónoma de PueblaC. Alvarez, A. Fernandez, O. Martinez, H. Salazar
Universidad Michoacana de San Nicolás de HidalgoL. Villasenor
Universidad de GuanajuatoDavid Delepine, Victor Migenes, Gerardo Moreno,
Marco Reyes, Luis Ureña UC Irvine
G. YodhUniversity of New Hampshire
J. Ryan
HAWC Design
900 tank array
4.3m high x 5m diameter tanks
100 MeV photons shown
Through-going Muon
150 m150 m
150
m15
0 m
HAWC: Background Rejection
Gam
mas
Pro
tons
Size of Milagro deep layer
Energy Distribution at ground level
Size of HAWC
Rejection Parameter: nPMT/cxPEnPMT = # PMTs in eventcxPE = Maximum # Pes in PMT > 30 m from fit core location
Background rejection
• Background rejection improves improves with increasing energy
• S/B 5x at E> 5 TeV (with rejection vs. no rejection)• Essentially background free near 100 TeV
hadrons
gammasMilagro
HAWC
Fra
ctio
n bk
gd r
emai
ning
HAWC DC Sensitivity: 5-Year Survey
IACTs 50 hrs (~0.06 sr/yr)IACTs 50 hrs (~0.06 sr/yr)
1 yr1 yr
EAS 5 yrs (~2EAS 5 yrs (~2 sr) sr)
2000 km
2000 km22 sr
hr sr
hr
Sensitivity vs. Source Size
€
Sextended ≈ Spoint
σ source
σ detector
Large, low surface brightness sources require large fov and large observation time to detect.
EAS arrays obtain ~1500 hrs/yr observation for every source.
Large fov (2 sr):
Entire source & background simultaneously observable
Background well characterized
Brenda DingusHAWC Review - December 2007
AGN Monitoring• Measure TeV duty factors and notify other observers of flares in real time.
• Unbiased survey for TeV “orphan” flares• All sources within ~2 sr will be observed every day for ~ 5 hrs.• Continuous observations – no gaps due to weather, moon, or solar constraints. • HAWC’s 5 sensitivity is (10,1,0.1) Crab in (3 min, 5 hrs, 1/3 yr)
Worldwide Dataset of TeV Observations by IACTs of Mrk421
1 month
Tank Details• PMT at bottom of tank• Non reflective interior surfaces• Roto-molded tank issues
– Largest tanks available not deep enough– Too large for road transport (build on site)
Steel pipe with bladder
No size limitations, easy transportation (in pieces)
@ Sierra Negra
In CA
Conclusions• Water Cherenkov Technology enables a “low”-threshold all-sky
gamma-ray capability (sub-TeV)• First generation instrument built at moderate altitude demonstrated
the capability of the technique– Discovery of Galactic diffuse emission at 10 TeV (large excess observed)– Discovery of extended sources of TeV emission– Discovery of an anomalous component to the local cosmic rays– TeV counterparts to Fermi GeV sources (5 new TeV sources)
• The next generation instrument will have ~15x greater sensitivity– Build at high altitude (4100m)
• Scientific Goals– Origin of Galactic Cosmic Rays– Understanding Galactic accelerators (Pevatrons)– Extragalactic accelerators via multi-wavlength/messenger study of transients
• Active Galaxies (10x Crab in 3 minutes)• Gamma-ray bursts
• Funding received for R&D and site development ($1M)– 3 tanks operating on site– All permits for full array in place
• Proposal at NSF and DoE awaiting PASAG (Summer 2009)