Transcript miniHAWC

Scientific Objectives of HAWC
Brenda L. Dingus
Los Alamos National Lab
Brenda Dingus
HAWC Review - December 2007
HAWC Scientific Goals
• Constrain the origin of cosmic rays via HAWC’s
observations of g-rays up to 100 TeV from discrete
sources and the Galactic plane.
• Probe particle acceleration in extreme magnetic and
gravitational fields via HAWC’s observations of
transient TeV sources, such as gamma ray bursts
and supermassive black holes.
• Explore new TeV physics via HAWC’s unbiased sky
survey with a detection threshold of ~30 mCrab in
two years.
Brenda Dingus
HAWC Review - December 2007
Galactic Sources of Cosmic Rays
• Galactic Cosmic Rays extend to >1000 TeV (at least to the knee).
• Gamma rays will be produced up to >100 TeV by these cosmic rays.
• Gamma rays produced by Inverse Compton scattering of electrons will
be suppressed by K-N effects.
• HESS observes hard spectra sources, but are these the accelerators of
cosmic rays? If so, their spectra should extend to > 100 TeV.
• HAWC has the sensitivity to measure spectra to the highest energies.
HESS Survey of the Inner Galaxy Reveals Extended Sources
with average spectra of dN/dE=kE-2.3
Brenda Dingus
HAWC Review - December 2007
HAWC Energy Resolution
• Shower Fluctuations
Dominate Energy
Resolution
• Higher Altitude of HAWC
increases # of particles
by ~6x
• Ability to measure a high
energy cut off is a
combination of the
energy resolution AND
the statistical error in the
flux
Brenda Dingus
HAWC Review - December 2007
HESS J1616-508
0.2 Crab @ 1 TeV
=-2.3
Highest energy
~20 TeV
Brenda Dingus
HAWC Review - December 2007
HESS J1616-508
0.2 Crab @ 1 TeV
=-2.3
Highest energy
~20 TeV
Simulated HAWC
data for 1 year
with no cutoff
Brenda Dingus
HAWC Review - December 2007
HESS J1616-508
0.2 Crab @ 1 TeV
=-2.3
Highest energy
~20 TeV
Simulated HAWC
data for 1 year
with 40 TeV
exponential
cutoff
Brenda Dingus
HAWC Review - December 2007
Galactic Sources are Extended
S extended  S point
 source
 detector
EAS ~0.5o IACT ~0.1o

HAWC’s large fov of 2 sr:
Entire source &
background are
simultaneously observable
Background is well
measured
Brenda Dingus
HAWC Review - December 2007
Galactic Diffuse Emission
• Hadrons are correlated with
matter density and the flux of
hadrons is strongly
constrained by direct cosmic
ray observations
• Flux from electrons is less
constrained, but must
decrease at highest energies
due to K-N effects
• HAWC + IACTs will detect
additional localized sources to
extract true diffuse emission
• HAWC will measure the
spectrum and spatial
distribution to constrain the
electronic and hadronic flux of
cosmic rays outside the solar
neighborhood
GALPROP Conventional (solid) and
Optimized (dashed) Models
Hadronic Pion
Decay
Electron Inverse
Compton
Scattering
Milagro
Observation
Brenda Dingus
HAWC Review - December 2007
Extragalactic Science: HAWC & Transients
• Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs)
– Bright Flares
– Rare Events
• Large Field of View, High Duty Factor Observatories are
required
EXAMPLE: PKS J2155-304
(z=0.117) flared to 50x
quiescent flux in one hour
with dN/dE=kE-3.5 which
would be detectable by
HAWC (6 ) as well as the
moderate state observed in
prior weeks
HESS Obs
of 2155-304
Brenda Dingus
HAWC Review - December 2007
10-6
HAWC & GLAST Transient Sensitivity
10
10-
10-8
GRB
<1 MeV
12
10-
TeV AGN
flares
GLAST and HAWC
sensitivity for a
source of spectrum
dN/dE=KE-2
z=0
z=0.1
z=0.3
z=0.5
no E cutoff
Eexp~700GeV
Eexp~260GeV
Eexp~170GeV
Brenda Dingus
HAWC Review - December 2007
HAWC example GRB lightcurve
•
•
•
High Energy cut off
could occur due to
absorption in GRB or
in transit via EBL
interaction.
Measurements of
lightcurve reveal
information about
progenitor, such as
bulk Lorentz factor of
the ejecta.
Best constraints on
Lorentz invariance
from initial peak of
the lightcurve.
HAWC lightcurve of a bright GRB (1e-4 ergs/cm2
fluence). Weaker burst counts scale with fluence.
Brenda Dingus
HAWC Review - December 2007
GRBs
• Milagro searches data within few seconds for short duration transients
and sends alerts to GCN, but has found no significant emission
• HAWC’s low energy response allows dimmer GRBs at more distant
redshifts to be observed
Brenda Dingus
HAWC Review - December 2007
TeV Emission From Short & Long GRBs
Long Bursts >2 sec
Neutron Star Binaries Coalescence
~1/2 with z<0.5
Not Observable by IACTs
Supernova of Massive Star
Few % with z<0.5
Observable by IACTS after >50 sec
F(z)
F(z)
Short Bursts <2 sec
z
z
Brenda Dingus
HAWC Review - December 2007
Active Galactic Nuclei
•
•
•
Open questions
– Protons or electrons?
– Plasma Bulk Lorentz factor?
– B-field?
– Location of g-ray production?
– Acceleration mechanism?
HAWC observations
– Many flares from known TeV AGN
– New TeV AGN
– Spectra > 1 TeV
– Multiwavelength Observations with
other wide field observatories & by
rapid notification
HAWC science
– Average Flux & Spectra
– Duty Cycle
– Unbiased Survey
– Constraints on Extragalactic
Background Light (EBL)
Brenda Dingus
HAWC Review - December 2007
AGN Monitoring
• HAWC will obtain duty factors and notify multiwavelength observers of
flaring AGN in real time.
• All sources within ~2 p sr would be observed every day for ~ 5 hrs.
• HAWC’s continuous observations would not have 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
Brenda Dingus
HAWC Review - December 2007
Mrk 421 with Milagro
Milagro and XTE ASM 7 yr lightcurve of Mrk 421
(Smith et al. ICRC 2007)
Crab Flux
1/1/2000
1/1/2001
1/1/2002
1/1/2003
1/1/2004
1/1/2005
1/1/2006
1/1/2007
ASM Flux
cts/s
Milagro - Events/day
• Milagro has observed 7yr lightcurve of Mrk 421
• HAWC’s increased sensitivity would result in ~10x smaller
error bars and have similar error bars on hour time scale
rather than 64 days
MJD - 50000
Brenda Dingus
HAWC Review - December 2007
Nearby AGN
• M87 is a known, variable source of TeV g-rays
– HAWC will detect average flux at 5.8extending spectra to highest
energies & monitoring variability
• Auger’s evidence for a correlation of UHECR with AGN point to other
nearby particle accelerators
– UHECR directions are deflected by several degrees, so individual
sources can’t be determined
– However, UHECR will produce TeV gamma-rays near the sources
due to interactions with the CMB & infrared
– HAWC can search the 100s of nearby AGN to find UHECR emitters
Auger’s 27 UHECRs
(black circles) > 6e19eV
& nearby, z<0.018, AGN
(red *) plotted in
Galactic coordinates
with the SuperGalactic
plane indicated by the
dashed line
Brenda Dingus
HAWC Review - December 2007
Cosmology from EBL Absorption
•
•
•
HESS & MAGIC constraints on the EBL
require the intrinsic spectrum of AGN is
very hard (G=-1.5)
– HAWC will increase the # of sources &
the # of flares from the same source to
decouple source dependent effects
Highest Energy Spectra constrains longest
wavelength EBL
– HAWC’s Spectra to > 10 TeV
measures the dust temperature &
impacts Galaxy Formation theories
Pair Halos around AGN probes EBL at
different ages of Universe
– HAWC’s all sky survey of extended
objects is required to find these halos
e-
~TeV g
e+
~eV g
Brenda
HAWC
IACT Dingus
HAWC Review - December 2007
GLAST
Surveying the TeV Sky
• Discovery Potential
• Many Classes of Potential
TeV Sources
– Extended Sources
• Dark Matter, Galaxy
clusters, AGN Pair
Halos, Molecular
Clouds, . . .
– Variable Sources
• Compact Binaries,
Microquasar Flares,
Solar Energetic
Particles, . . .
Brenda Dingus
HAWC Review - December 2007
Astrophysical Sources
• Known TeV sources such as x-ray binaries and microquasars
– HAWC will monitor for flares and for periods difficult for IACTs (such
as the 3.4 year period of PSR B1959-63 in which periastron aligned
with the full moon)
• Postulated TeV sources such as Galaxy Clusters & GLAST sources
– HAWC’s field of view contains 100s of Galaxy Clusters within z<0.1
and will constrain the TeV flux of Galaxy Clusters as a class of TeV
emiters
– >1/2 of GLAST sources will be within HAWC’s field of view
HESS x-ray binary obs. & HAWC’s sensitivity
Brenda Dingus
HAWC Review - December 2007
Exotic Sources
•
Particle-Antiparticle Annihilation
• WIMP neutralino, c, is postulated by SUSY
• 50 GeV< mc< ~ TeV
c
q
or gg or Zg
q lines?
c
• HAWC can survey >2p sr for potential dark matter sources—
nearby clumps, dwarf galaxies, clusters
• HAWC will monitor Galactic center for variability (a definite
indication that the source is not dark matter)
• Primordial Black Hole Evaporation
• As mass decreases due to Hawking radiation, temperature
increases causing the mass to evaporate faster
• Eventually temperature is high enough to create a quark-gluon
plasma and hence a flash of gamma-rays
• HAWC’s continuous observation of >2p sr is necessary to find
these transients
Brenda Dingus
HAWC Review - December 2007
Summary
• HAWC’s sensitivity will allow new observations
leading to new understanding of the high energy
Universe
– Highest Energy HAWC Observations constrain
origin of cosmic rays
– Wide field of view, High Duty Cycle probes the
transient TeV sky
– Unbiased survey of >2p sr has discovery potential
for new TeV physics
• HAWC’s scientific investigations are complementary
and enhance the scientific return of other current and
planned particle astrophysics observatories
Brenda Dingus
HAWC Review - December 2007