Upload
gordon-williams
View
218
Download
0
Tags:
Embed Size (px)
Citation preview
LOFAR Cosmic Ray KSP
Heino Falcke Radboud University, Nijmegen
ASTRON, Dwingeloo
What we (don’t) know about UHECRs
We know:their energies (up to
1020 eV).their overall energy
spectrum We don’t know:
where they are produced
how they are producedwhat they are made offexact shape of the
energy spectrum
Potential Sources
Hillas plot: Gyro radius has to fit source size!
Galactic < 1017eVSupernovaeneutron stars & stellar
black holes
Extragalactic >1018 eVSupermassive black holesGamma-Ray burstsIntergalactic shocksTop-down: decay of
primordial superheavy particles (?)
1 EeV = 1018 eV
eB
ER CRgyr
Radio Images of Cosmic Accelerators
Cas A
Cygnus A
Fornax A
NRAO/AUI
1.4 , 5, & 8.4 GHz
The Pierre Auger Observatory
Auger: Clustering of UHECRs
The beginning of “charged particle astronomy”!
AUGER Collaboration (2007), Science9. Nov. (2007)
Ultra-high Energy Cosmic Ray Spectrum
The Pierre Auger Collaboration, Physics Letters B (2010)
?
Auger Composition Results
Looks like CR
primaries become
more heavy.
NB: HiRes
experiment
interprets this
differently (=> only
protons)
prediction for iron nuclei
proton prediction
Auger Data
Dep
th o
f sh
ow
er
maxim
um
in
atm
osp
here
Cosmic Rays in the Radio
νMoon
S. Lafebre
Radio Astroparticle Physics:
Cosmic Rays in atmosphere: Geosynchrotron emission
(10-100 MHz) Radio fluorescence and
Bremsstrahlung (~GHz) Radar reflection signals (any?) VLF emission, process
unclear (<1 MHz) Neutrinos and cosmic rays
in solids: “Cherenkov emission” (100 MHz - 2 GHz) polar ice cap (balloon or
satellite) inclined neutrinos through
earth crust (radio array) CRs and Neutrinos hitting
the moon (telescope)
LOFAR Cosmic Ray KSP: Main Goals
Understand High-Cosmic Rays Measure and fully characterize radio signals of extensive air showers
(e.g., reference calibration for LOFAR and AUGER). Understand effects of and on lightning Use radio technique in transition region from Galactic to extragalactic
CRs to clarify their nature (i.e., composition) Search for radio flashes from the moon to characterize UHECR
spectrum at highest energies (NuMoon) Develop the techniques to work on raw time series data on
dipole-level (transient buffer board & tied-array beam) in near field and far-field.
Science Synergy with other KSP Transients: Identify and understand other sporadic signals (“RFI”,
lightning, SETI, astrophysical sub-ms pulses, e.g. giant pulses) Survey: Identify sources of UHECRs
Coherent Geosynchrotron Radio Pulses in Earth Atmosphere
UHECRs produce particle showers in atmosphere
Shower front is ~2-3 m thick ~ wavelength at 100 MHz
e± emit synchrotron in geomagnetic field
Emission from all e± (Ne) add up coherently
Radio power grows quadratically with Ne
⇒ Etotal=Ne*Ee
⇒ Power E∝ e2 N∝ e
2
⇒ GJy flares on 20 ns scales
coherent
E-Field
show
er front
e± ~
50 M
eV
Geo-synchrotron
Falcke & Gorham (2003), Huege & Falcke (2004,2005)
Tim Huege, PhD Thesis 2005 (MPIfR+Univ Bonn
Earth
B-Field
~0.3 G
Cross Calibration of LOPES10 and KASCADE
B-field
Distance
UHECR Particle Energy
Horneffer-Formula 2008
Energy and Composition from MC Simulations
Huege et al. 2008, (Astropart. Phys.) - REAS2 code
lateral radio profile Xmax radio flux N
e
~5% shower-to-shower
fluctuations
LOPES Data
(Horneffer et al. 2007)
LOPES-KASCADE
Imaging of CR radio pulses with LOPES
See also Falcke et al. (LOPES collaboration) 2005, Nature, 435, 313
Horneffer, LOPES30 event
A. Nigl 2007, PhD
Nanosecond Radio Imaging in 3D
Off-line correlation of radio waves captured in buffer memory
We can map out a 5D image cube:3D: space2D: frequency & time
Image shows brightest part of a radio airshower in a 3D volume at t=tmax
and all freq.Bähren, Horneffer, Falcke et al. (RU Nijmegen)
Actual 3D radio mapping of a CR burst
No simulation!
UHE Neutrino detection needs large detector volumes!Auger: Aeff=3000 km2, Moon: Aeff=9×106 km2
Back to the moon …
Cosmic Ray
100 MHz Radio Waves
Westerbork antennas
Westerbork Synthesis Radio Telescope
Westerbork (WSRT) Experiment
4 freq.
bands
4 freq.
bands
UHE Neutrino Limits from WSRT νMoon Experiment
nMoonAnita ‘08
Buitink et al. (2009), A&A - Scholten et al. (2009), Phys. Rev. Lett.
LOFAR Sensitivity to Neutrinos
Singh et al. (2009)
LOFAR sensitivity to CRs
Singh et al. (2009)
Commissioning Results:Triggering finally works
Horneffer/Corstanje/Falcke (Radboud)
Station Pulse Triggers in a Day (Sky Distribution)
A. Corstanje (Radboud)
LOFAR low-band has all-sky visibility!
5ms All-Sky Imaging with LOFAR TBBs
Single LBA station
S. Welles
L. Bähren
(Radboud)
5ms All-Sky Imaging with LOFAR TBBs
Single LBA station
S. Welles
L. Bähren
(Radboud)
Real-Time Detection and TBB Dumping of Crab Giant pulse
Time
Fre
qu
en
cy
Dispersed Pulse
Sander ter Veen
LOFAR Air Shower Array
Layout:
5 clusters of 4 particle detectors
in LOFAR core
RFI measurements in ASTRON’s antenna
chamber
Will provide CR triggers to core stations
Hardware & DAQ software is ready, testing under way, installation is next
Synergies with other KSPs
Technical:Identification of steady nearby and transient RFI sourcesDipole-based antenna calibration and monitoring (gain,
polarization)TBB software (mainly with TKP)
Scientific;TKP: FRATs – triggering and identification of Fast Radio
TransientsSurveys: Make survey products accessible to CR
communityCatalog of radio sources with estimates of sizes, magnetic
fields, jet powers …
Summary & Conclusions
We want to explore the fastest time scales in LOFAR (down to 5ns) and develop novel techniques in radio astronomy Real-time triggering Transient Buffer-Board (TBB) utilization 3D all-sky imaging on buffered data (1sec observation needs 1TB of data to be processed…) Transient signal extraction
detect airshowers from UHECRs between 1017 and 1019 eV determine radio properties with unprecedented quality (e.g., input for AUGER) determine precisely energy and composition in the suspected transition region form Galactic to Extragalactic
CRs
search for UHECRs and Neutrinos >1021 eV hitting the moon Verify GZK-cutoff at the very least place the best limits on super-GZK CRs and neutrinos (which SKA will surely
detect) investigate and search for other sub-second signals in buffered data and collaborate
with Transient KSP Giant pulses of pulsars coherent burst from exploding neutron stars, etc. Lightning SETI (One Second All-Sky Survey)
provide a catalog of northern UHECR source candidates with Survey KSP.