very high energy astronomy cosmic ray · called ‘2nd order fermi acceleration’ or short ‘2nd...

http://personal.inet.fi/koti/tom.eklund/aurora.html

Very High EnergyAstronomy

brief summary of lecture available at:http://ihp-lx2.ethz.ch/AstroTeilchen/

Dr. Adrian Biland / [email protected]

HPK E24, 044 633 2020

15.May.2009 A.Biland: Very High Energy Astronomy 2

Cosmic RayOrigins


pppp

Charged Particles deflected by omnipresent magnetic fields …

!!

Need Photons (or Neutrinos) to be able to identify sources


Location of Sourcespropagation of highest energetic protonsin galactic B-field (galactic plane):

If protons > 1020eV exist, they can beused to do ‘CR-Astronomy’ ....

Latest results from AUGER indicate that at least perpendicular to the galactic

plane, the effect of galactic magnetic field is much smaller

==> CR-Astronomy already possible at ~1019 eV ???

(But: if particles are Fe (as indicated by AUGER measurements), AUGER

result would ask for extremely low intergalactic B-field

Maybe reason for AUGER anisotropy is just based on the structure of the B-

field of our Galaxy: low field perpendicular to the plane ==> less shielding

power than for extragalactic particles coming along the galactic plane)


AUGER (south)

black circles: all events >1018eV seen by AUGER (3o error)red stars: position of nearby AGNs (<200Mpc)==> seem correlated ==> nearby AGNs could be sources of >1018eV particles ==> no problem with GZK

Science,9.11.07

This is no proof that nearby AGNs (Active Galactic Nuclei: galaxies with huge

central black holes ‘swallowing’ large amount of material) are the real sources.

High density of AGNs probably indicates regions with high mass-density and

high dark-matter content

==> result indicates that highest energy particles come from nearby

(extragalactic!) regions with high mass density

Any possible type of cosmic accelerator could be the source

Ruled out:

-galactic origin (would expect to concentrate in galactic plane)

-isotropic distribution


Key Questions

Distribution of sources: - few bright point-like sources ? - many faint sources/ diffuse ?Type of sources: - astrophysical (“stars”,fields) ? - new physics (decay of heavy part.)?

Location of sources:nearby (solar system) ?galactic? extragalactic? universal?


Location of SourcesFrom p+X --> "0+Y , "0 --> ! ! Search for ! with characteristic spectra(mainly at rather low energies...)

==>1) ~same CR everywhere in our Galaxy ==> (probably) not local/solar origin 2) far less CR in Large Magellanic Cloud ==> not extragalactic/universal origin


Location of SourcesFrom magnetic field strengths:

==> [for GeV … TeV energies]

1) CR can enter/escape solar system ==> (probably) not solar origin

2) CR confined/shielded by galactic field ==> not extragalactic origin


Location of Sources

Most probably, main componentof CR has galactic origin

(arguments not valid for highest energies: - low contribution to "0 production - can escape/enter galactic field ==> highest energy CR probably extragal.)


Acceleration Mechanism?

CR acceleration process(es) must explain:

-how to reach huge particle-energies-how to reach high fluxes-power-law in spectra E-2.7 up to knee, but because of easier ‘leakage’ at high energies, assumed initial spectrum ~E-2.1


Collisionless Acceleration(first proposed by Fermi 1949):

Assume a particle with velocity v scattersat (magnetic) cloud moving with velocity uwith |v| >> |u|

Not collision with a single molecule, butelastic(!) scattering with whole cloud (m~!)

What’s the particle energy after scatter ?15.May.2009 A.Biland: Very High Energy Astronomy 12

Collisionless AccelerationMust average over all scattering angles …

Rough estimate:take average of extreme cases, classical

Case 1:#E1=0.5m(v+2u)2-0.5mv2

=0.5m(4uv+4u2) > 0Case 2:#E2=0.5m(v-2u)2-0.5mv2

=0.5m(-4uv+4u2) < 0Average:#E =0.5(#E1+#E2)= 4mu2

in average: pos. energy gain

magnetic

magnetic


‘2nd Fermi’Rough estimate: #E ~ 4u2

relativistic treatment, averaging over all

angles ==> #E ~ 8/3u2

(for particles having v >> u ==> need rather high energy seed particles ?!! )

2nd order process (u2) ==>

called ‘2nd order Fermi acceleration’

or short ‘2nd Fermi’

Why so interesting ?


‘2nd Fermi’

Assume many scatterings e.g. on many magnetic bubbles[looks like multiple scattering in normal matter]

after n scatterings: total gain =n#E==> can reach any Energy

(if initial seed particles exist ....)


‘2nd Fermi’Assume, particles have probability P toescape the acceleration region after eachscattering (= acceleration step)

==> after step k:

Ek = E0 + k#E Nk = PNk-1 = PkN0

==> power law spectrum !!!


‘2nd Fermi’- can reach high energies- automatically produces power law- can produce large flux (high energydensity in astrophysical B-fields)

but:very slow: - (#E/E ~ (u/v)2, u << v ) ==> gain very little energy per scatter


‘1st Fermi’Look for 1st order (linear) process: #E ~ u

static

B-field

e.g.: reflection on shock front (can have strong B-fields)and back-reflection from static B-field(magnetic cloud)

#E = E2-E1 = 0.5m(v+2u)2-0.5mv2

= 2m(uv + u2) ~ uv v>>u

#E/E ~ uv/v2

~ u/v

But: need very extended,strong B-field to deflect very high energies ???


Cosmic AcceleratorsMaximum energy that can be reached byFermi acceleration is defined by the sizeand strength of a B-field region(if curvature radius > size ==> all particles escape, no further acceleration possible)

Estimates claim that galactic sources cannot accelerate to >1015eV,hypothetical extragal. sources not >1018eV

But recent results indicate that <B> wasunderestimated ==> higher acceler.possible?


'Hillas' Plot:

Magn. field vs.size of mostenergeticastrophys.object classes

100 EeV= 1020eV 1ZeV= 1021eV

?

?

x LHC


MeasuringVery High Energy

Photons


Cosmic microwave background, ~3 mm

satellites

rockets

ra

dio

tele

scopes

" - rays

Earth surface

optical

Telescopes Cherenkov telescopes

particle detectors

fluorescence detectors

ballo

ons

The windowsof Astronomy 50% of incident

radiation absorbed

3 1026 Hz

"-rays

"-rays

For which wavelengths is it possible to measure photons from ground ?


X-ray and !-ray Astronomy

!

e+e–

Focusing instruments Coded masks, collimators(i.e. INTEGRAL)

Compton telescopes

COMPTEL

Pair conversion telescopes

(until ~300 GeV)

keV MeV GeV

XMM

Newton

Energies above few 100eV, no materials known that could work as lenses etc.

==> need other techniques to identify the direction of flight of a photon to be able

to identify (point like) sources of radiation

One could use long narrow tubes/collimator systems, but this would limit the FoV

as well as resolution to opening angle of the device

X-rays can be reflected on very small angles ==> possible to focus if using huge

instruments

few MeV: use complicated system of transparent and blocking regions (‘coded

masks’) ==> pattern of passing photons tells position of source

>10MeV: use Compton effect: MeV photon induces emission of lower energy e-

in upper detector (--> 1.Position). In lower detector, absorb the MeV photon (-->

Energy, 2.Position --> Direction). Spatial resolution limited by scattering angle of

photon (can be estimated by knowing energy of e- in upper detector)


Pair Conversion Principle (Satellite)

ca

lori

me

ter

tr

acke

r

A

C s

hie

ld

!

e+e–

EGRET

Three main parts:

An “active shield”against chargedcosmic rays (particledetector set in anti-coincidence)

A tracker todetermine thetrajectory of the e±

A calorimeter formeasuring theenergy.

EGRET (on board of COMPTON GammaRay Observatory-Satellite 1991-2000)

Pair conversion: GeV photon produces e+e- pair; these can be measured with

standard particle physics detectors and therefore the initial direction and energy

of the photon be reconstructed (within resolution of the detector)

==> each individual photon can be measured ==> 3 detected photons from same

point in the sky can be sufficient to identify a source (for low diffuse background

flux)


R. Dubois, SLAC

GLAST/FERMI MissionGLAST measures the direction,energy and arrival time ofcelestial gamma rays

LAT measures gamma-rays in theenergy range ~20 MeV - 300 GeV(There is no experiment now covering this range)

GBM provides correlative observations oftransient events in the energy range~20 keV – 20 MeV

Orbit: 550 km,

28.5o inclination

Lifetime: 5 years

(minimum)

Launch: June 2008

significant improvements compared to EGRET

LAT: Large Area Telescope [main instrument]

GBM: GLAST Burst Monitor


GLAST LAT, Sketch of a Tower

12 layers Si +

3% X0 of Pb

4 layers Si +

18% X0 of Pb

2 layers Si (no Pb)

0

17

0

7

8 layers CsI

Each TKR layer consists of2 Si layers rotated by 90°(X,Y) and Pb plates

Thin Pb

Thick Pb

Blank (no Pb)

Each CAL layer consists of12 crystals and each layeris rotated with respect withthe next so that it canprovide X and Ymeasurements! Detector

silicon microstrip detectors allow very precise measurements of particle

trajectories

Energy measured in calorimeter (very heavy ==> rather small total area ....)


DAQElectronics

Grid

Tracker

Calorimeter

ACD ThermalBlanket

•Array of 16 identical“Tower” Modules,each with a tracker(Si strips) and acalorimeter (CsI withPIN diode readout)and DAQ module.

•Surrounded by finelysegmented ACD (Anti-Coincidence Detector)(plastic scintillatorwith PMT readout).

GLAST LAT instrument

R. Dubois, SLAC


GLAST design goals

-Low profile for wide field of view-Segmented anti-coincidence shield (ACD) to minimize self-veto at high E.-Fine-segmented calorimeter:enhanced background rejection and shower leakage correction.-High-efficiency, precise track detectors located close to the conversions foils to minimize multiple-scattering errors.-Modular, redundant design.-No consumables.-Low power consumption (580 W)


Old vs. New Space Detectors

B. D

egra

nge

Caution about usually quoted high-energy limit of the energy ranges:

GLAST will be able to measure a 300GeV photon if it hits the detector. But even

for the brightest known sources, GLAST will only catch very few photons

>100GeV during 10 years of operation because of intrinsically limited size of such

satellites...


Old vs. New Space Detectors


FERMI (formerly known as GLAST)

4 daysskymap!!!

3 month skymap: already better than EGRET 10y sensitivity (just published, >200 pointlike sources…)

The FERMI 'bright source list' is not yet an official catalogue

Since spectral and temporal informationl missing, difficult to compare with

EGRET catalogues (FERMI will publish first catalogue in Sept. 2009)

For sure, FERMI will deliver very interesting results ….

(and from Sept. 2009 on, all data will become public !!!)


FERMI: Pulsars

FERMI already discover new class of pulsars ….


FERMI: Pulsars

Must be somewherea calibrationproblem inEGRET and/orFERMI …

Vela-Pulsar

FERMI already discover new class of pulsars ….


FERMI: GRBsGRB080916C, z~4.2first clear indication forGRB emission >1GeV …

New hope for GRB detections with ground based VHE telescopes …


Limitations of Space-bound !-rayTelescopes in the VHE Range

-Small effective areas result in extremelylow detection rates at E >30 GeV, evenfor strongest sources :

$Crab,E>30GeV ~ 0.2 photons/cm2/year

-Calorimeter depth !10 radiation lengths,corresponding to ~ 1 ton per m2

(which is already very expensive to put into orbit …)

==> showers leak out of the calorimeter ==> limited Energy-resolution


Advantages of Space-bound !-rayTelescopes in the VHE Range

• No background (CR vetoed)

• Large field of view (FOV)

• Full sky coverage

• 100% duty cycle

• Rather good angular resolution• Rather good energy resolution

Cover detector with e.g. scintillators

==> if (charged) CR particle crosses detector, it leaves signal in scintillator

==> veto ==> background-free

Problem: shower-particles can escape calorimeter and hit veto-counter


Alternatives to Space-bound!-ray Telescopes in VHE Range ?

!-rays produce air-showers like charged CR==> is it possible to use air-shower detectors to measure !-rays ???

Main Problem:Charged CR much more abundant (~105)than !-ray ==> how to distinguish ???

Ground based instruments are orders of magnitude less expensive, but can they

do the job ???


Extensive Air Showers (EAS)

Electromagnetic Hadronic

Electromagnetic showers are more regular and better confined

Electromagnetic showers do not contain muons


Shower front evolutionShower particles form roughly a disk-shaped front (or very flat cone) of few ns thickness, traveling at speed"c towards the ground

Sketch of shower development

Use arrival time distribution to estimate direction of incident particle

Use intensity of signal to estimate energy of incident particle


Tibet Air Shower Array

To improve gamma-identification sensitivity of EAS detectors: increase size of

total detector as well as reduce distance between individual detector stations.

Additionally go to higher altitudes to be closer to the shower maximum ==>

catch more particles


Tibet Air Shower ArrayFurther improvement:

use better coverage of detector area==> ARGO-YBJ 75x78 m2 RPCs (under construction)

RPC: Resistor Plate Chamber

Allows to cover rather large area without major gaps for reasonable price


Water Cherenkov Detectors

MILAGRO: -full detection coverage -some CR rejection (µ-detection)

idea: second layer of PMTs only sensitive to muons (did not really work out; later

abandoned)


MILAGRO

upgrade: using ‘outriggers’ (cherenkov water tanks)

Using simple water tanks with one PMT significantly enhances area (~20000 m2)

==> higher sensitivity


MILAGRO

northern sky (MILAGRO), status 2007

2007

2003


MILAGROextendedregions ofbright TeV! emissionfrom the‘Cygnus’region(crosses: unident. EGRET contours: expected "0 from CR+ ISM)


Near(?) FutureProposed ‘MILAGRO upgrade’:

High Altitude Water Cherenkov (HAWC):

- higher altitude (4000m a.s.l. ?) ==> lower E-threshold ( 700 GeV ?)

- larger area ==> higher sensitivity (factor 10 ?)

a.s.l. : ‘above sea level’


Status of VHE-! Air Shower Detectors

Advantages:- high duty cycle- large field of view/full sky coverage- possibility to see extended sources- high energy- large active area

Disadvantages:- limited CR rejection ==> low sensitivity- high energy threshold (TeV)


Measurement of Gamma Rays

Air-shower detectors have too low sensitivity andtoo high energy threshold(but are interesting because of ‘full’ sky coverage)

How to improve ???

Needed:

- lower energy threshold (i.e. see showers not reaching ground ?!?!?!)

- better gamma/hadron separation

==> how to reach ???

Main problems are:

- gamma-hadron separation, since there are far more hadronic than photonic

showers

- angular resolution ( O(degree) ) ==> difficult to identify sources

Main advantage:

- ‘full’ sky coverage (at least northern or southern hemisphere); not possible with

other ground-based detection techniques


Cherenkov Effect

First seen by Marie Curie:all radioactive sourcesshowed similar blue gloomin water … ???

Explained by P.Cherenkovin his PhD Thesis (1934):


Cherenkov EffectMedium, refractive index n

Charged particle with v < c/ntraverses medium==> local, shorttime polarization of medium

Reorientation of electricdipoles results in (very faint)isotropic radiation


Cherenkov Effect

v > c/n==> radiation from different points along the trajectory arrive in phase within narrow light-cone at the observer ==> bright light

Similar to sonic boom if v > cacoustic

cos # = 1/$n


Cherenkov Effect1948: P.M.S. Blackett suggests:

shower particles are highly relativistic;refractive index of air > 1

==> must radiate Cherenkov light

huge CR-flux==> CR-induced Cherenkov light contributes O(10-4) of total night sky light (during new-moon)

[ duration of flash of individual shower O(3 ns) ]


Cherenkov Radiation of Shower

( %&1 for 21 MeV e- )

(simplified)

v>c/n; $ = v/c > 1/n; $min=1/n

(for $ ~ 1)

E=" mec2

in water:

E ~0.775MeV

Detailed explanation of Cherenkov radiation can be found in many textbooks (e.g.

Jackson: “Classical Electrodynamics”

For modern experiments, treatment of atmosphere much more complicated

(taking into account temperature, humidity, ....)


Cherenkov Radiation of ShowerAt higher altitudes: lower air-density==> refractive index closer to 1==> smaller Cherenkov-angle==> rather flat distribution of !cherenkov on ground



Hump-structureindependentof initialenergy,as long asshower diesout beforereachingobserver(not true if E >> 1TeV)



for each e- inthe shower !!!

energy loss by Cherenkov radiation ~ 5000 times less than by ionization

(fluorescence light), but because of beamed direction easier to distinguish from

night-sky background


Cherenkov Radiation of ShowerNot all !cherenkov reach observer:1) Rayleigh scattering (by air molecules)


Cherenkov Radiation of ShowerNot all !cherenkov reach observer:2) Mie scattering (by dust particles)


Cherenkov Radiation of ShowerNot all !cherenkov reach observer:3) Absorption (by Ozone, H2O, … )


Cherenkov Radiation of ShowerNot all !cherenkov reach observer:==> have to measure 300…700 nm



primary particle enters atmosphere

produces air-shower

shower-particles emit !cherenkov ==> light pool

detector anywhere in light pool sees shower

problem: background light...

And biggest problem: how to distinguish hadronic and photonic showers


Sampling Cherenkov Telescopese.g.: operational(2007): STACEE, CACTUS (USA), ... decommissioned: GRAAL (Spain), CELESTE (France), …


Sampling Cherenkov TelescopesSecondary optics concentrates !cherenkovfrom each heliostat into a dedicated PMT ==> measure !chr distribution on ground


Sampling Cherenkov Telescopes

STACEE





Advantages: - huge mirror area ==> low energy threshold, good energy resol. - excellent pointing - inexpensive (daytime: powerplant; night: telescope)Disadvantages: - tiny FoV (difficult for searches) - limited directional choice - limited gamma/hadron separation ==> large BG - short duty cycle (need dark nights, good weather)

==> no new VHE source found with this technique(but spectra of few known sources extended to lower energies)



How to improve ?

- need dedicated telescopes for free pointing- need larger FoV (at least few degrees)- need better gamma/hadron separation [how to get more information about the shower parameters than just distribution of Cherenkov-light on ground ???]

- need money ....... (and brilliant ideas)


Imaging Cherenkov Telescopes

1st generation (since ~1950)

directional light-collector + fast camera + trigger+ DAQ ==> …

Crimea

Harwell

light collector: increase number of collected cherenkov photons

fast, high sensitivity camera: able to measure very shorttime light-flashes

Trigger: electronics to identify fast flashes in real-time

Data AcQuisition (DAQ): write triggered signal to storage medium for detailed

offline analysis



2nd generation:

a) WHIPPLE-telescope (Arizona, USA):

10m tesselated main reflector (Cotton-Davies = spherical)

Pixelized PMT-camera

Operational 1968 - …

(several upgrades (mainly camera improvements); 2nd telescope added, but too low quality => never used)

Usually diameter is given as size of reflector ( ==>taking into account gaps,

WHIPPLE ~70m2 collecting area)



WHIPPLE:1989: breakthrough (after 21 years of operation) first VHE source found (Crab) (ApJ, 342:379-395, 1989)key ingredients:use ‘high resolution’ PMT camera (39 PMTs)use precise Monte Carlo simulations==> detailed image analysis to reject CR


Imaging Cherenkov TelescopesAt higher altitudes: lower air-density ==> refractive index closer to 1 ==> smaller Cherenkov-angle(==> rather flat distribution of !chr on ground)

==> direction of !chr correlated with height of emission


Imaging Cherenkov TelescopesCherenkov-Telescopesdo not measure!chr-distributionon ground, butmeasure (fractionof) total showerdevelopment==>can be used toidentify/rejecthadronic showers


Hillas - ParametersAdditional parameters:

SIZE = Integral (~energy)

CONCentration

= % of signal within

highest N pixels

ASYMmetry

= signal(<dist) /

signal(>dist) (head / tail)

LEAKage

= % of signal in

outermost pixels (edge of camera)

Definitions:


Hillas - Parameters

Definitions: ‘alpha’ correlatedto shower direction(parallel to telesc.- axis: alpha = 0)

Hadron-showers showflat alpha-distribution

Assume VHE gammas coming from source pointed at with the telescope ==>

have alpha ~0

Hadronic showers come from all directions ==> have flat alpha distribution

==> looking at potential source for extended time, expect a peak at 0 in alpha

distribution

Problem: much more hadronic events ==> takes (too) long time to get (tiny)

signal out of statistical fluctuations

==> use other Hillas parameters to reduce number of hadronic showers in the

sample


Hillas - Parameters

!,e: single electromagnetic shower

p: collection of many electromagnetic sub-showers (plus hadronic core plus muons) [ p+X "0 + "-"+ ... !! µ e

==> p-shower images are typically wider and less smooth than !-shower images

==> statistically, expect different images


Hillas - Parameters(for single telescope)

Very High Energy( > 100 GeV):

!- and hadron-showers showrather differentdistributions forHillas parameters ==>good hadronrejection

Caution: exist far more hadron showers !!!15.May.2009 A.Biland: Very High Energy Astronomy 76

Hillas - Parameters(for single telescope)

Below ~100 GeV:

!- and hadron-showers showrather similarHillas-parameters(hadron-showers consistof fewer subshowers;more statist.fluctuations)

==>hadron rejectionfar more difficult

Caution: exist far more hadron showers !!!

MAGIC (and soon MAGIC-II and HESS-II; later CTA) try to reduce energy

threshold far below 100 GeV

Much more difficult than expected few years ago ....

15.May.2009 A.Biland: Very High Energy Astronomy 77(W.Hofmann, HESS)

1/10000 s (100 µs)

1/100000 s ( 10 µs)

1/1000000 s ( 1 µs)

1/10000000 s

(100 ns)

1/100000000 s

( 10 ns)

Fast Camera is important !

Night Sky

Background ~ 100 Million

photons (in same

wavelenght-band

as cherenkovlight)

hit each PMT

per second

(new-moon night;

much more with

partial moonlight)

Cherenkovflash(for low energy)

~100 photons

distributed over

~4 PMTs


1/10000 s (100 µs)

1/100000 s ( 10 µs)

1/1000000 s ( 1 µs)

1/10000000 s

(100 ns)

1/100000000 s

( 10 ns)



1/10000 s (100 µs)

1/100000 s ( 10 µs)

1/1000000 s ( 1 µs)

1/10000000 s

(100 ns)

1/100000000 s

( 10 ns)



1/10000 s (100 µs)

1/100000 s ( 10 µs)

1/1000000 s ( 1 µs)

1/10000000 s

(100 ns)

1/100000000 s

( 10 ns)



1/10000 s (100 µs)

1/100000 s ( 10 µs)

1/1000000 s ( 1 µs)

1/10000000 s

(100 ns)

1/100000000 s

( 10 ns)




Use (expensive) readout electronics (FADCs):

VERITAS: 2ns (2006) MAGIC: 3ns (2003) --> 0.5ns (2007)

==> camera time-resolution shorter than duration of cherenkov-flash ==> additional information to distinguish between hadron and gamma showers (MAGIC: improve sensitivity ~50% )

[‘DOMINO’ chip developed at PSI will significantly lower the cost]


Air Shower Pictures

Statistically,different showertypes producedifferent showerimages ==>try to get rid ofnon-gammashowers

(WHIPPLE)15.May.2009 A.Biland: Very High Energy Astronomy 84


WHIPPLE: Crab (1989):

Rather difficult to convince people(after many false-detections by other experiments…)

On: point telescope to potential VHE source

Off: point telescope to region in sky from where no VHE expected



WHIPPLE: Mkn421: Nature, 358,477-478,1992

2nd source found: Extragalactic (AGN)

improved analysisand more data ==> also muchmore convincingsignal from Crab

Active Galactic Nucleus:

Galaxy with huge central Black Hole (109 solar masses), large accretion disk and

huge jets perpendicular to the disk (see later)


Imaging Cherenkov TelescopesCAT (France):1996-2000

pioneering fine-pixelPMT-camera: only 5m reflector, but 546 PMT-camera

==> better imageparameter reconstruction

(==> WHIPPLE upgraded accordingly)


Imaging Cherenkov Telescopes‘HEGRA System’La Palma, 1996-2000

5 telescopes,each 3.5m reflector,271 PMT pixel camera

pioneering ‘stereo approach’



Stereo Approach:Several telescopes (separated 80...150m)measure the identical shower(all telescopes ‘sitting’ in same light pool)

==> possible to reconstruct 3dimensional image of the shower

==> better hadron rejection better angular resolution better energy reconstruction

(but: more telescopes = higher cost ...)

4 telescopes observing individual showers: improve statistics by factor 4

==> gain in sensitivity =sqrt(4) = 2

4 telescopes observing identical showers stereo: statistics not improved

(even lowered), but better hadron rejection

==> gain in sensitivity >3


Imaging Cherenkov Telescopes2000: ~10 sources foundmost by Imaging Air Cherenkov Telescopes (IACT)

Next step (3rd generation telescopes): start data-taking WHIPPLE VERITAS (4x12m) 2007 CAT HESS (4x12m) 2004 HEGRA MAGIC (1x17m) 2004 CANGAROO CANGAROO-III 4x10m 2002(first experiment in southern hemisphere)

Upgrades going on: MAGIC: 1x17m ---> 2x17m stereo (2009) HESS: 4x12m ---> 4x12m + 1x28m (2010 ?) CTA?: ~100 telescopes 24m, 12m, 6m south+northern site


VHE Detectors 2007:


Imaging Cherenkov TelescopesAdvantages: - ‘good’ !/hadron separation - good pointing capability - high sensitivity (huge active area) - rather low energy threshold

Disadvantages: - small FoV (cannot do full-sky) - short duty cycle (dark, clear nights) - more expensive than sampling telescop. (but much cheaper than satellites)


H.E.S.S. “High Energy Stereoscopic System”

http://www.mpi-hd.mpg.de/hfm/HESS/ (main contributors: Germany, France )

Khomas Highlands, Namibia, 1800m asl


H.E.S.S.Southern site optimal for observation ofgalactic sources ( SNR, PWN, surprises...)(especially around galactic center)

Phase I:-4 x 12m telescopes, 120m separation; square-aluminized glass mirrors; round; 60cm-spherical dish; f/d = 1.2-high-resolution PMT-camera, 5o FoV

(original plan Phase-II --> 16x12m replaced by construction of 1x28m )


H.E.S.S.

HEGRA

HESSHESS basicallyblown-up copy ofHEGRA telescopeswith CAT-cameras

known technology==> can immediat.start datataking


H.E.S.S.Many important new discoveries within first few years of operation:

-scan of inner part of our galaxy

-first millisecond-pulsar in VHE (no pulsation)-dark accelerators-high-redshift AGNs


VERITAS“Very Energetic Radiation Imaging Telescope Array System”

http://veritas.sao.arizona.edu (main contributors: USA, UK, ...) located at Mt.Hopkins parking lot; Northern site

artist view


VERITASFirst 3rd generation proposal

Phase I:- 4 x 12m telescopes;- spherical; round glass mirrors- high resolution PMT-camera; 3.5o FoV- blown-up carbon copies of WHIPPLE- 500MHz FADCs

Original plan for Phase-II: 7x12mabandoned ....


VERITAS-known hardware (1st telescope ready since 2003)-very experienced physicists (WHIPPLE)-terrible problems with: - founding (many $$$ into GLAST) - location(s): already 2nd location had to be abandoned because of legal problems with native americans; operate from parking lot...

==> limited physics outcome yet (but catching up fast; today, most sensitive array)


CANGAROO-III“Collaboration of Australia and Nippon for a GAmma Ray Observatory in the Outback” (3rd upgrade)

http://icrhp9.icrr.u-tokyo.ac.jp/ Whomera, Australia (170m asl !!!)


CANGAROO-III

1x 3.8m ---> 1x 10m ---> 4x 10m

- First telescope in southern hemisphere- First 3rd generation telescope starting datataking (2002)

Big problems with: - telescope hardware (e.g. mirror ageing, lightning destroyed electronics, ...)

- analysis reliability (many ‘discoveries’ disagree with HESS; several cross-checks with MAGIC confirm HESS)

===> unknown status & future ...

Let’s hope they will recover soon !!!

Don’t forget: at first, HUBBLE was a complete failure ....


MAGIC“Major Atmospheric Gamma-ray ImagingCherenkov” Telescope

http://wwwmagic.mppmu.mpg.de/Main contributors: Germany,Spain,Italy,Switzerland, ...location: Roque de los Muchachos, Canary Islands, 2200m asl

Switzerland (ETH) joined October 2003 (at inauguration), i.e. no influence on

design and construction ....


MAGICNorthern site optimal for extragalacticsources: AGN, galaxy-clusters, GRBs

Phase-I:1x 17m dish; parabolic; f/d=1quadratic mirrors: aluminum on honeycombhigh-resolution PMT-camera, 3.5o FoV ( 1.8oTrigger )

300MHz FADCs ( ---> 2GHz )a lot of new technology ==> needed more time to understand the system

(today, lowest energy threshold of all CherernkovTelescopes)

Problem: need long time to understand the hardware and systematic effects ==>

less efficient than H.E.S.S. (also less than 50% of money available)

Side remark:

in past, very heated discussion between H.E.S.S. and MAGIC design:

HESS: many medium-sized telescope (initial design: 16x12m) for stereo

MAGIC: few large telescopes (17m, abandoned plan for a 30m)

Today: HESS going for a single(!) 28m telescope


MAGIC Support StructureKeep total

weight as low

as possible to

allow for fast

repositioning

!

use carbon-fibrecell-structure :

strong, but not

very rigid

!Mirror segments

will defocus

when moved

! need AMC


Future PlansCurrent 3rd generation telescopes proofVHE sky much richer than expected fewyears ago

Need:- higher sensitivity (more sources)

- lower energy threshold (distant sources)- higher max. energy (highest energy/source)- better energy- and angular- resolution

(correlation with other wavelengths, morphology of sources, ...)


Very Near Future

MAGIC: 2nd telescope incommisioning-phase==> soon stereo

2010(?): upgrade MAGIC-I camera with higher sensitivity photo-sensors

MAGICMAGIC

MAGIC-IIMAGIC-II

Picture taken June 2006Picture taken June 2006


Very Near FutureH.E.S.S.: build 28m telescope by 2010 (but rather low sensitivity photo-sensors)

12m 28m 12m

option to include a AMC still under discussion…


Near(?) Future‘Cherenkov Telescope Array CTA’: (pan-european project)goal: - improve sensitivity by factor >10 - increase energy coverage by factor >10

==> need ~100 telescopes

==> must reduce cost per telescope15.May.2009 A.Biland: Very High Energy Astronomy 108

Mid FutureOther plans: use much higher sensitivity photo- sensors

e.g. APDs as used in CMS

relative

sen

sitivity

G-APD

PMTs andimprovements

Recent measurements done by our group show that the values from

HAMAMATSU (used for the plot) are too optimistic [by ~20%]

Also new PMT develompments under way

But: one of the two PMT producers worldwide just went out of business (Feb.

2009)


Mid FutureETH [our institute] +PSI have lot ofexperience in using APD (140’000 in CMS)

==> very ambituos goal: build a firstG-APD camera by 2010together with PSI, Uni Wurzburg, Uni Dormund;mount camera in refurbished 3m HEGRA telescope to gainexperience; use this telescope for dedicated observations

Tests with prototype of first camera-module just started …

If successful: important for CTA upgrades

For next few years, PMT are much cheaper per cm2 than G-APDs

But G-APD prices could drop significantly when produced in large amount (since

they will probably be used in medical equipment, huge demand possible)


Near Future

==> DWARF


Detector Sensitivities

CTA (?)

HESS,MAGIC


"-Origins


Top-Down Scenario

HE and VHE gamma could originate from:

- decay of very heavy particles;

(topological defects)

==> would contribute to diffuse radiation; do not expect point sources

[New Physics...]

(soon a AUGER publication ruling out Top-Down also forhighest energy charged CR)

Several HE and VHE sources identified, but we cannot (yet) measure how much

they contribute to the flux of charged Cosmic Ray (CR) particles.


Bottom-Up ScenarioVHE gamma get energy from interactionof VHE/UHE charged particles:

e-, p, (ions) + - Matter - Radiation (low energy !) - B-fields (see Pulsars)

"-

"0

"+

!! (TeV)

p+ (>>TeV)

matter Inverse Compton

! (TeV)

e- (TeV) Synchrotron! (eV-keV)

! (eV)

B


e- Interaction with B-Field

combined effects:‘Synchrotron-Self-Compton effect’ (SSC)

e- beam in B-field produces !synchrotron that get additional energy by IC with e- from same beam (not necessarily identical e-)

==> synchrotron radiation (~keV) and IC radiation (VHE) are coupled ==> |B|


Exist Point Sources ?

What about VHE ?

We know from EGRET there exists many point-like sources (galactic and

extragalactic) of HE gamma-rays.

Are there also sources of VHE gamma-rays ???

If yes: are they correlated ???


EGRET <--> VHE ?

Trevor Weekes (2002): (Spokesman WHIPPLE)

“If you concentrate too much on the EGRET, you might miss a crucial part of the full picture”


EGRET <--> VHE ?“You can find many pictures of egrets, many pictures of elephants, but only few pictures of egrets and elephants”T.Weekes

Only few EGRET sources are also strong at VHE

Many VHE sources have not been seen by EGRET

EGRET: <10GeV (old)IACTs: >300GeV

==> important to close the gap:

GLAST/FERMI; MAGIC,HESS,VERITAS,(CTA)


! from PeV 'Accelerator'

EGRET/ IACTFERMI

similar 2-bump structure for electrons (SSC)


GalacticVHE " Sources


Where to Look ?Search for (rather) unknown sources of CR

At the moment, full-sky monitoring devicesnot sensitive enough. (FERMI >10GeV ?)

Observe only some selected candidates ?==> very biased results

Best compromise:scan a rather small region of the sky,but also look at selected interesting objects

see http://www.mpi-hd.mpg.de/hfm/HESS/ (H.E.S.S.) and http://wwwmagic.mppmu.mpg.de/ (MAGIC)


Where to Look ?Scan will still be biased- is selected region characteristic- difficult to see weak sources- difficult to see very extended sources- difficult to distinguish sources along sameline of sight

- ...

btw: background limited observation ==> sensitivity ~ sqrt(observ.time) !!!


Where to Look ?Central part of our Galaxy has highestdensity of possible source candidates

Equatorial plane tilted vs. milky-way ==> central region best observable from southern hemisphere ==> H.E.S.S. (scan +/- 30o)

btw: latest observations indicate our galaxy is not a pure spiral like Andromeda,

but has a central bar ...


Galactic Sources2003: only 3 galactic VHE sources known2004: scan of the galactic center region with the H.E.S.S. telescope:

Exposure Time:

ApJ 636 (2006) 777-797

Two special regions have much longer exposure time, because extended

observation of specially interesting objects done.


Probably, there are far more weaker sources. But would need more observation

time ....

(There are many other interesting objects in the sky)


CR Power Requirements

Power needed to maintain (galactic) CR:

CR Energy-density: ~1eV / cm3

CR density: ~stable >108 years CR age (@few GeV): ~107 years(~lifetime)

L = (Volume)*(E-density)/(lifetime) ~ "(15kpc)2(200pc) * 1eVcm-3 / 107y ~ 5 1040 erg/s = 5 1033 J/s

If a body is directly exposed to CR, the chemical composition at it’s surface

gets modified by spallation processes.

Comparing chemical composition at surface and inside of e.g. moon-stones

(concentrating on abundances of long-living radioactive isotopes and their

decay products), one can conclude that CR intensity has not drastically

changed over long time


1) Supernova (SN)Already 1911 (before Hess showed extraterrestrial origin !)

Zwicky postulated SN as sources for CR !

Kinetic Energy emitted by typ-II SN:

Typically, ~10Mo ejected, v~5 108 cm/sOn average: 1 SN / 30 years in our Galaxy

==> LSN ~ 3 1042 erg/s = 3 1035 J/s

==> have to convert few% of kinetic SN Energy into CR-Energy (reasonable ?)

==> SN are candidates for CR sources ?(more than 99% of total SN Energy emitted in form of neutrinos ==> ' Astronomy?!)


Supernova Remnant (SNR)Models show that (type-II) Supernovae usually produce two shock waves; v1 < v2 (shell-type SNR)

Energy loss at outer shock:#E1 = 2m(-v1v)

Energy gain at inner shock:#E2 = 2m(v2v) , v>>v2>v1

#E=#E1+#E2=2mv(v2-v1)#E/E = 4(v2-v1)/v


Supernova RemnantShock waves from SN have typicallifetime ( ~ 1000y , v1,2 ~ 106m/s

Energy gain per cycle: En+1=En(1+))Escape Probab. per cycle: P

===> spectral index ! ~ P/) ...===> Supernova Remnants (SNR) seemexcellent accelerators up to ~100 TeV(B-field ~0.1G ==> larmor radius too large...)

VHE photons must be emitted by higher energetic charged particles

==> detection of VHE photons assumed to be proof for particle acceleration

But looking into details, many open questions …. (see next week)


Identified SNRImportant question:e- or p assource particle?

e.g. RXJ 1713Contours: X-ray (ASCA)

Colour: VHE (H.E.S.S.)

[Nature 432(2005)]

excellent spacialagreement ofemission morphology==>indication for e- (?)

For SSC model (e-), expect highly correlated X-ray (synchrotron) and VHE

(inv.Compton) radiation


Identified SNR

but X-ray and VHE spectra do not really agree for simple SSC models (neither in shape nor in intensity)

VHE spectrum good fit with"0 prediction ==> p beam dump(?)[no correlation with X-ray needed]

RXJ 1713


Identified SNR

Contours: VHE emission (HESS)

Color code: mass distribution(?) ( CO-emission )

==> disfavors proton model ... ?!?!?!?!==> need more sources to understand ....

RXJ 1713

For beam-dump, expect highest VHE radiation from regions with highest mass

density

Spacial origin of VHE radiation: agrees with e-, disagrees with p

Spectrum of radiation: disagrees with e-, agrees with p

My personal view: all acceleration models discussed in the literature are

oversimplified ==> must be wrong (or at least: incomplete)

Acceleration probably includes turbulent magneto-plasma-hydrodynamics that is

far from understood even in the laboratory


2) Neutron Star (NS)Shrinking core of progenitor starAngular momentum conserved ==> *NS ~ 2"/30ms (rNS ~ 20km)

Special case: ‘Pulsar’ Strong, short radio and X-ray pulses with extremely precise timing

Slow deceleration: #T/T ~ 10-14


Neutron StarRotational Energy: Erot ~ 1043 J

Energy loss (deceleration): #E~ -0.3 1028J/s

Lifetime: ( ~ 108 y

#NS in Galaxy: n ~ 106

==> total Energy emitted: n#E ~ 1034J/s compare #ECR ~ 5 1033J/s==> NS could maintain CR (if acceleration!)

( but Pulsars also expected to emit comparable energy by gravity waves ? )


Neutron StarFast rotation, huge B-field (>>1012G)

If B tilted relative to * ==> spinning B-field --> strong E-field

max. value: E ~ 1015V/mi.e. charged particle can gain 1000TeV/m !

NS can transform Erot into EkinCR…But: can CR escape NS region ???


Neutron StarProblem: huge B-field ==> Gyro-radius (Larmor-radius) r[km] = E[MeV] / 30*B[G]

i.e. E = 100 TeV = 100 106 MeV B = 1012G r = 3 10-5km = 3mm !!!

==> particles can not escape ! (?)


Neutron StarElectrons immediately lose energy by Synchrotron-radiation (far less efficient for Protons)

Also VHE photons can not escape becauseof Magneto-pair production: !VHE + B --> e+ e-

!VHE + B --> !+ !


Neutron Star

Photons can onlyescape close tomagnetic polesof Neutron Star

==> pulsation

Exist two models for the escape of high-energy particles from Pulsars:Outer gap ; Polar cap/Slot gap(regions where conditions of B and E field could allow escape of particles and/or VHE photons)


Red:Polar Cap

Blue:Outer Gap

Full:Young Pulsar

Hashed:Old Pulsar


Crab PulsarDepending on model, pulsed emission shouldhave cutoff at few 10 GeV; finally seen byMAGIC in 2008!

Polar cap completelyruled out; but alsoouter gap model hasdifficulties to explainmeasurement

pulsed emission

Pulsed emission seen by EGRET for several Pulsars up to ~10GeV

Different Pulsar models predict different cutoff energies for same object.

VHE measurement of one single pulsar gives more information about pulsar

models than >1000 pulsars meaured with extreme precision with radio

telescopes…


Pulsar-Wind-Nebula Plerion / Pulsar Wind Nebula (PWN): SuperNova remnant or nearby high density cloud disturbed by huge energy outflow from Pulsar

Crab (SN1054)

Charged particles accelerated in huge (rotating) B-field of Neutron star

Probably, the beamed, relativistic mass outflow from neutron star induces shock-

wave in SNR and disturbs spherical symmetry

PWN shock-wave accelerates CR particles to extremely high energies via Fermi

acceleration

==> p and/or e- emit VHE photons

Also possible that a relativistic particle beam travels much farther and is dumpedinto a rather far away gas cloud (producing beamed "0), or inducing shock-waves

and acceleration-processes there. Even a photon-beam might be able to induce

shock-waves in distant gas-clouds.


Identified PWN Crab well known in all wavelengths,also by EGRET very close (~2kpc) ==> very bright

found by WHIPPLE, seen by ‘all’ experiments

no other known candidate on line of sight =>no doubt

Crab is used as ‘standard’ candle in VHE observations

Measured fluxes and experimental sensitivities often given relative to Crab-flux

(advantage: the large, unknown systematic uncertainties cancel)

Crab is a northern source, badly visible for southern experiments like HESS


Possible PWNSeveral sources from the HESS scan haveknown pulsars ~nearby, but no proof theseare the accelerators that light up theVHE emission; some sources are extended.

( Beamed relativistic emission from strong pulsars could travel rather long distance until VHE gamma emission is initiated:

- high matter density: shock waves - high B-field: SSC mechanism from e-


Possible PWNTwo sources on nearly same line of sight(but could have large separation in distance)

color: H.E.S.S. ; triangles: positions of known pulsars

telescoperesolution(PSF) ==>extendedsources

Point Spread Function (PSF)


Possible PWNTriangles: known PulsarsWhite circles: known SNR

White dotted: unid EGRET

point-likesource foldedwith experimentresolution

==> extended15.May.2009 A.Biland: Very High Energy Astronomy 146

Possible PWN

HESS J1834:(cross-checked MAGIC)

some agreement withhigh mass density regions(contours) could beindication for abeam-dump ....[higher resolution VHE images would be helpful, but intrinsic limit of IACT technique]

Imaging Air-shower Cherenkov Telescope (IACT)


3) Binary SystemsBinary systemof a largestar and acompact,heavy object(Neutron star or Black Hole)

Mass transferfrom largestar tosmall object


Binary Neutron StarConstant matter flux from star speeds upthe rotation of Pulsar ->‘millisecond Pulsar’

Known to emit ~1031 J/s (per system) in X-ray

If similar amount of Energy emitted in CR==> few 100 Binaries could make major contribution to total CR Energy


Binary Neutron StarEnergy gain in Binary system:Gravitational acceleration of proton:

#E=-!G mpMNS/r2dr=G mpMNS/RNS~ 70MeV

But mass flow >>1030 protons / second ==> huge total energy to be emitted

Same processes like on Neutron Stars,plus additional acceleration processespossible in accretion disk (e.g.shock waves)

Physics in accretion disk highly controversial

RNS

Inf.


micro-QuasarBlack hole instead of Neutron star==> even more gravitational Energy pumpedinto accretion disk

relativistic jets perpendicular to accr.disk(similar as in real Quasars, but factor 106 smaller dimensions …)==> can be used as laboratory-model ofQusars ?!!!


X-ray BinariesTwo possibilities for VHE production:micro-Quasar: Pulsar Wind Nebula:form. of accretion disk emission from pulsar interactsand relativistic jets with the ‘atmosphere’ of the(like in real Quasars) heavy star (mass flow and light)

VHE emission from Quasars: see next week


X-ray BinariesX-ray Binaries

variablevariable flux: flux: [orbital phase][orbital phase]

--marginal detection [0.2-0.4] marginal detection [0.2-0.4] (X-ray?)(X-ray?)

--maximum flux atmaximum flux at [0.5-0.7] [0.5-0.7] (Radio?)(Radio?)

(~16% (~16% of Crab flux)of Crab flux)--orbital modulationsorbital modulations (==>emission is produced in the(==>emission is produced in the interplay of interplay of both objects ?)both objects ?)--low emission at low emission at periastron periastron [0.2][0.2]-hints for periodicity-hints for periodicity ??????

(no measurements [0.8-1.0] and [0.0-0.1] (no measurements [0.8-1.0] and [0.0-0.1] because because of coincidence with full moon )of coincidence with full moon )

Science 312, 1771 (2006)Science 312, 1771 (2006)LS I +61 303 (MAGIC detection)

Can only observe 1-2 hours per night for few months per year ...

Seems better correlation with Radio emission than with X-ray (but not enough

VHE and X-ray data yet to take a conclusion)


X-ray BinariesX-ray Binariescompanion: B0 companion: B0 Ve Ve star with star with circumstellar circumstellar disc, 10.7mag; disc, 10.7mag; distancedistance 2kpc2kpchighly eccentric orbit(0.7); highly eccentric orbit(0.7); period=26.5dperiod=26.5d (from X-ray and radio modulation)(from X-ray and radio modulation)compact jets (100AU) resolved in radio;compact jets (100AU) resolved in radio; marginally assoc.marginally assoc. EGRET source EGRET source Radio-bursts at phase [0.5-0.8], X-ray burst around [0.3]Radio-bursts at phase [0.5-0.8], X-ray burst around [0.3]

(assuming(assuming periodicity...) periodicity...)

Green contours: positional uncertainty of unidentified EGRET sources


X-ray BinariesLS 5039: ( science 309, 746 (2005)

similar object(?), detected by HESS

3.9 days orbit;excellent agreement withX-ray periodicity

discussions going on if these objects shall be renamed !-ray binaries

(probably more energy emitted by !-rays than by X-rays)


X-ray Binaries

not only flux, but also spectrum depends on orbital phase;ev. interaction of VHE and optical photons ?

LS 5039


4) Galactic CenterGalactic black hole (~106 Msun):shock-waves and strong B-fields==> accelerator ????

but also many other objectsin very crowded area couldbe accelerators ....


Galactic CenterVHE emission claimed byWHIPPLE, CANGAROO, HESSbut completely incompatiblespectra ==> who is correct ?

==> measured byMAGIC (only possibleunder very large zenithangle ==> Ethreshold~1TeV)

==> excellent agreement with HESS,CANGAROO ruled out

Spectral shape and no indication for cutoff up to >10TeV excludes (most) Dark

Matter models as dominant source for the radiation

(see later)


Galactic Center

not possibleto decide (yet)

about originof VHEradiation

MAGIC and HESS: no indication for variability on month/years-scale (else could rule out SNR)

SNR (and PWN) are expected to show constant emission

Black hole induced emissions can show dramatic variability (see next week), but

also have steady emission for long time


Galactic Center RegionAdditionally fromextended HESSmeasurements:

after removing signal from point-sources, clear indication for~diffuse radiationfrom the vicinityof the galacticcenter;good agreement withmass distribution==> CR beam dump ?

J1747: PWN

J1745: GC(?)


Galactic Center Region

Taking into account thesteepening of spectrumbecause high energyprotons can leave thegalactic mag.Field,VHE spectrum still indisagreement withmeasured CR-spectrum

==>indication for recent/ongoing CR production ?!

If diffuse emission would be induced from beam-dump of galactic CR, the

observed spectrum should agree with predictions from the ‘Diffuse model’.

The observed deviation can indicate the emission is not induced by CR, or the

CR spectrum close to the galactic center is different than in our neighborhood

(e.g. close to a very strong CR source, the average CR age is much lower and

therefore the spectrum harder [highest energy particles had not yet enough time

to escape])


5) 'Dark Accelerators'Some VHE sources foundhave now known astro-physical counterpart !!!(but has nothing to do with Dark Matter or Dark Energy)

White circle and triangle:nearby SNR; can not bethe accelerator

But: could exist nearbypulsar (not visible if weare not in emission direction)


Galactic VHE sources 2007

galactic VHE sky is far richer than expected .....

Source Type Discovery reference

Crab Nebula PWN Weekes et al., ApJ 342 (1989) 379

PSR 1706-44 PWN Kifune et al., ApJL 438 (1995) L91

Vela X PWN Yoshikoshi et al.,ApJL 487 (1997) L65

RX J1713.7-3946 SNR Muraishi et al., A&A 354 (2000) L57

Cassiopeia A SNR Aharonian et al., A&A 370 (2001) 112

TeV 2032+4130 ? Aharonian et al., A&A 393 (2002) L37

RCW 86 SNR Watanabe et al.,28th ICRC (2003) 2397

Sgr A* ??? Tsuchiya et al., ApJL606 (2004) L115

G0.9+0.1 PWN Aharonian et al., A&A 432 (2005) L25

MSH 15-52 PWN Aharonian et al., A&A 435 (2005) L17

RX J0852.0-4622 SNR Katagiri et al., ApJ 619 (2005) L163

HESS J1303-631 PWN Aharonian et al., A&A 439 (2005) 1013

PSR 1259-63 Bin Aharonian et al., A&A 442 (2005) 1

HESS J1614-518 ? Aharonian et al.,Science 307(2005) 1938


HESS J1640-465 SNR? Aharonian et al.,Science 307(2005) 1938


HESS J1813-187 SNR Aharonian et al.,Science 307(2005) 1938

HESS J1825-137 PWN Aharonian et al.,Science 307(2005) 1938



LS 5039 Bin Aharonian et al.,Science 309(2005) 746

LSI 61+303 Bin Albert et al., Science 312 (2006) 1771

HESS J1632-478 ? Aharonian et al., ApJ 636 (2006) 777




HESS J1713-381 SNR Aharonian et al., ApJ 636 (2006) 777




Source Type Discovery reference



Westerlund 2 OC Aharonian et al., A&A 467 (2007) 1075

HESS J0832+058 ? Aharonian et al., A&A subm.

MGRO J1908+06 ? Abdo et al., ApJ 664 (2007) L91



MAGIC J0616+025 ? Albert et al., ApJL accepted

W28 SNR Aharonian et al., in prep.

HESS J1912+101 PWN Aharonian et al., in prep.

Cygnus X-1 Bin Albert et al., ApJL 665 (2007) L51

HESS J1427-608 ? Kosack et al., 30th ICRC, Merida, 2007






HESS J1857+026 ? Kosack et al., 30th ICRC, Merida, 2007

HESS J1858+020 ? Kosack et al., 30th ICRC, Merida, 2007

HESS J1908+063 ? Djannati et al. 30th ICRC, Merida, 2007

Kes 75 PWN Djannati et al. 30th ICRC, Merida, 2007

G21.5-0.9 PWN Djannati et al. 30th ICRC, Merida, 2007

HESS J1357-645 PWN Lemiere et al., 30th ICRC, Merida, 2007

HESS J1809-193 PWN Lemiere et al., 30th ICRC, Merida, 2007

Type Candidates:

SNR (shell-type) Supernova Remnant

PWN Pulsar Wind Nebula / Plerion

Bin Gamma-ray Binary / Microquasar

OC Open Cluster

? Unidentified, incl. ‘Dark Accelerators’

also: diffuse emission from Galactic Center Region

few new sources found in 2008; expect ~20 new ones from HESS later this year

(improved analysis of the galactic-scan data)


Stellar Wind ???HESS:‘Westerlund 2’ is a young stellar cluster containing manyheavy stars (==>strong stellar winds?).Possible explanations for VHE source could be collidingstellar winds forming shock-waves ....

extended

If this is correct, it would be the first galactic VHE object having ‘normal’ stars as

initiator of the acceleration.

All other identified galactic sources have SNR or PWN as origin (i.e. remainders

of a SuperNova explosion)

Starburst regions believed to be interesting, because they are expected to host

quite many SuperNovae ==> many SNR and PWN as accelerators. But it

seems, that already before the Supernova explosion, VHE acceleration is

possible


Extra-GalacticVHE " Sources


Where to Look ?Search for (rather) unknown sources of CR

At the moment, full-sky monitoring devicesnot sensitive enough at VHE

Observe only some selected candidates ?==> very biased results

But only possibility ...


Galaxy Classification

Active

Galactic

Nucleus

LBL HBL

Milkyway,

Andromeda,

...

Exist other (incompatible)classification schemes …

HBL are a tiny fraction of all galaxies, but assumed best candidates to look for

VHE emission


Active Galactic Nuclei (AGN)Huge (108-1010Mo)Black Hole withhigh mass inflow

==>

Accretion-disk,two relativisticjets

Variable inflow==>variable emissionsin what energy regime?


AGN ClassificationMost probably,the differentAGN-classes justindicate underwhat angle welook at theobject ...

BL-Lacs:look directlyinto one of the relativistic jets==> expecthigher energiesfrom Lorentz boost


Spectral Energy Density (SED)dependencies between different wavelengthscan help to understand basic mechanisms

radio optical Xray EGRET IACT FERMI

Coloured and black data from different observation periods ==> significant

varibility in VHE, X-ray, optical

Is there a correlation ???


AGN Morphology

Probably several shock waves in jet ==> several VHE sources ?!

radio

IACTs (and GLAST) have by far not good enough angular resolution to be able to

distinguish between possible emission from the core and the different ‘knots’ ...


AGN MorphologyAt least in radio(highest resolution),the emission cancome from several‘blobs’ that cantravel with differentvelocities along thejet axis

IACTs (and FERMI)have not good enoughangular resolution tosee such details==> see only average

Because of viewing angle, the different blobs seem to have velocities higher than

speed of light

(‘superluminal motion’)


AGN Variability

Four 3-years 'light-curves' (flux vs. time)of radio measurements with same telescope

Is there anything common ?


AGN VariabilityIt is the same source …

Longest measurement of an AGN with identical(!) telescope


AGN Variability

At least at lowenergies (optical,radio), AGNs show variabilityat any timescale(years<->minutes)


AGNs @ VHE ?Major questions:- which AGNs emit also at VHE ?- how do AGNs accelerate particles (thatemit VHE photons) ?

- how do AGNs look at VHE (spectra,variability, ...) ?

- correlations between VHE and otherenergies ?

- ...- but also: use VHE photons as tools toinvestigate fundamental physics questions(extreme energies@extreme distances; see next week)


AGNs @ VHEStatus 2003:~4 VHE emitters known (all HBL-type)

VHE flux highlyvariable:-intensity can change factor >>10: ‘flares’-variations seen on timescales ~ 1day

good agreement between experiments==> confidence in IACT method

existed also several dubious claims of other VHE AGNs, but most not confirmed

(and/or ruled out by new observations)


sometimes the spectral index changes with flux

AGNs @ VHE


often exists goodcorrelation betweenVHE and X-ray flux

but indication of ‘orphan flares’ (VHE without corresponding X-ray)

AGNs @ VHE


AGNs @ VHE

huge variabilities …=> need luck to catch a AGN in flaring state(most known sources invisible in 'low state')


AGNs @ VHE


AGNs @ VHEbiased because of ‘hunt for flares’}

exists a ‘quiet state’VHE emission, oronly during flaringactivity ??????

The old Whipple telescope is mainly used to monitor 'known sources' to get an

unbiased selection;

MAGIC is regularily monitoring few 'known sources' for same reason

ETH + Uni Wuerzburg + Uni Dortmund are refurbishing an old HEGRA telescope

for constant monitoring of the brightest VHE-AGNs in the northern sky….


AGN VHE ‘Dogmas’until ~2004, many people believed to‘know’ about VHE emissions from AGNs:

- only HBLs are potential VHE emitters ( ‘Blazar Sequence’ )- minimal timescale for variability ~ radius of central Black Hole ( ~1hour )- potential origin of VHE radiation must berather close to the central Black Hole


Only HBLs ???if you only look at HBLs, you will only see HBLs...

already HEGRA found hint for VHE emission fromthe giant radio-galaxy M87 (confirmed by HESS,MAGIC,VERITAS)

‘very nearby; mis-aligned Blazar ==> no real problem’

2006: MAGIC sees VHE emission from the LBL ‘BL Lacertea’2006: MAGIC sees VHE emission from the FSRQ ‘3C279’2008: VERITAS sees VHE emission from LBL/IBL ‘W Comae’===> ‘Blazar Sequence’ is dead !!!!

2009: HESS sees VHE emission from Cen-A (similar to M87 or first VHE-detection of a Seyfert ?)

HBL: high frequency peaked Bl-Lac object

LBL: low frequency peaked Bl-Lac object

IBL: intermediate frequency peaked Bl-Lac object

FSRQ: flat spectrum radio quasar


Only HBLs ???

Active

Galactic

Nucleus

LBL HBL

Milkyway,

Andromeda,

...

M87HEGRA, ... 3C279

MAGIC

BL LacMAGIC

.... more to come ....

In the case of Blazars, the relativistic jet is directly pointing towards the observer

==> if emission is coming from the jet, expect higher energies because of

Lorentz-boost


1h Shortest Variability ???From the two best (longest) investigatedVHE HBLs (until 2005):

- Mkn 501 exhibits strong flux variabilityon the month-year scale, but not shorter

- Mkn 421 exhibits stron flux variabilitydown to the minimal ~1h timescale

?? both objects should be rather similar ??


MAGICMAGIC

X-rayX-ray

OpticalOptical

full-moonfull-moonCrabCrab

Markarian Markarian 501501

Mkn501: nearby AGN, z = 0.034Mkn501: nearby AGN, z = 0.034- well known VHE source - well known VHE source (detected by WHIPPLE 1995)(detected by WHIPPLE 1995)-- has large flux variations has large flux variations ( O(20) on years scale)( O(20) on years scale)

MAGIC observationMAGIC observation scheduled to measurescheduled to measure ‘‘low-statelow-state’’ spectra in spectra in June/July 05June/July 05

but:but: strong VHE flares seenstrong VHE flares seen (X-ray counterpart ?)(X-ray counterpart ?)


Markarian Markarian 501501

AGN jets have sizes >105 LyBH has radius ~ 1 Light-hour

observer

2min bins

Mrk501

~similar

But variability within minutes==> small emission region or extreme boost factors

MAGIC

2min binwidth

Many people did not trust us ...


1h Shortest Variability ???

Later, H.E.S.S. alsofound short variabilityfrom PKS-2155==> no doubt possible(pure serendipity detections)

Shortest observed variabilities probably just limited by sensitivity of observatory

Observed very fast VHE variabilities are shorter(!) than what has ever been seen

in optical/radio/X-ray/... !!!

(because of huge active area of Cherenkov Telescopes, we can measure shorter

variations)


Spectral ShapeNot only flux canchange drasticallywith time, alsothe shape of thespectrum can varysignificantly==>every flare looksdifferent ???

try to find ‘quiet’ state ...

Mkn 421


Origin of VHE ???‘Misaligned Blazar’ M87: very close, not looking into jet ==> possibility to see the origin??

IACTs (and GLAST) have not good enough angular resolution

but doing Multi-Wavelength might help ???


Origin of VHE ???

M87: VHE vs. Xraycorrelation better ifassuming emissionfrom Core than fromblob HST-1 ?!!!

triggered by MAGIC


VHE @ AGN StatusMany excitingAGN resultsfrom the past4 years

analysis andobservations andtelescope improvgoing on ...

?


VHE @ AGN Status“There is something wrong with ...

... common assumptions about the gamma-ray generation mechanism

... common assumptions about the basic physical parameters of blazars

... common assumptions about the nature of TeV sources “

Esko Valtaoja, ‘Workshop on AGN and relatedFundamental Physics in VHE Astronomy’

Jerisjaervi, Finland, April 2008

Every theoretician has a different model that can ‘easily’ explain all observations

But all models get into trouble if trying to combine with results from radio and X-

ray

Need much more data; long-time and full multi-wavelength coverage

(still difficult to convince other astronomers: bright VHE sources usually ‘boring’

for radio, X-ray, ... )


Physics usingVHE "-rays


VHE as ToolEven if the sources and mechanisms ofVHE are not understood, one can tryto use them as tools to do physics inregions not accessible in laboratories.

Use- highest energy photons- longest distancesto investigate questions from cosmologyand fundamental physics ....


e.g. extreme B-fieldsIn the extreme B-fields close to e.g. thesurface of Pulsars expect Quantum-effects

- quantum-synchrotron radiation==> 'curvature radiation'

- magneto-pair production ( !+B --> e+e- )- etc.

Recent detection of the high-energy end of(V)HE emission from Crab-Pulsar by MAGICallows to test such predictions


e.g. Extragal. Background Light (EBL)

Universe is not transparent for VHE photons !!!

Usually people use the term ‘Extragalactic Background Light’ (EBL)

but correct term would be ‘Metagalactic Radiation Field’ (MRF)


EBL

Intrinsic spectrum + EBL density+ Distance = Measured spectrum

Intrinsic spectrum + EBL density+ Measured spectrum = Distance...

(but what is intrinsic spectrum ???)

==> IF(!) intrinsic spectrum is know [e.g. typical AGN spectrum], could serve as

independent method to measure huge distances with different systematics than

SN1a method ==> independent cross checks possible (Dark Energy !!!)


EBLDensity of CMB canbe measured [andcalculated] with veryhigh precision (WMAP)

Density of EBL cannot be measureddirectly: too highforeground contrib.from galactic objectsplus IR emission fromdetector

Redshifted Redshifted Redshifted

star light dust emission Big Bang

IR

Redshifted star-lightcontains info about all stargenerations since BigBang


EBL

Upper limit fromdirect measurem

Lower limit from‘galaxy count’:sum of all infowe have aboutknown astronom.objects


EBLKnown:-measured spectrum-distance (ident. AGNs)

Assumed (models):intrinsic spectrum can’tbe harder than 1.5 (?)

==> unfold measuredspectrum with differentEBL possibilities andcheck if intrinsic ok measured unfolded

Higher redshift AGNs show more absorption ==> better suited

Learned that current AGN models are too simplistic, so the assumption about the

intrinsic spectrum might be wrong

==> important to also measure (unabsorbed) nearby AGNs !!!


EBL

If assumptionabout intrinsicspectrum iscorrect, VHEmeasurementsalready excludehigh EBL density


EBL

VHE measurements start to touch lower limits ???


EBL

Because of 'extreme' redshift z>0.5, thespectrum of 3c279 contains most information (but unfortunately rather low statistics)

3C279

Unfortunately, 3C279 (like all AGNs) shows chaotic flaring behaviour

==> don’t know when one should observe

==> don’t know how long it takes to get higher quality data

==> Need higher sensitivity observatories !!!

3c279 is another AGN-type (FSRQ) than the usual HBLs

==> we know even less about the intrinsic spectrum …


EBL

When/if MAGIC gets more signal from3C279, expect much better constraints ...

3C279

But the detection of 3c279 already clearly proves the universe to be rather

transparent at VHE

==> huge potential for MAGIC-II, HESS-II, CTA, …


EBL StatusOpen question in cosmology: what was first ?- first star generations (from small star-size gas clumps) combine later to form a galaxy [these stars contribute to EBL; difficult to include in galaxy count]

- first galaxy-size gas clumps are separated into star-size clumps and then form first stars [i.e. already very first stars included in galaxy count EBL limit]

VHE observations indicate that lower limits fromgalaxy counts represent (almost) full EBL density(?)==> galaxies formed first ???

Are first stars created independently or as a complete galaxy ???


EBL StatusVery recent star-formation modelsshow that very first stars might havebeen fueled by DarkMatter annihilationinstead of H->He fusion

==> might have had different emission than normal stars==> would contribute to EBL different than assumed in predictions

high precision EBL results from Cherenkov telescopes could be theonly possibility to find evidence for ‘DarkMatter Stars’ ??

If Dark Matter is 'neutralino-type', such DarkMatter stars would have

masses >>100M_sun,

Radii >>1 Atronomical unit (150 Mio km) I.e. really huge, but low density

surface temp ~5000K (like sun), I.e. very cold for such heavy objects

lifetime ~ few Mio years; unclear what happens when all DM fuel consumed

(my personal opinion: collapse continues ==> 'standard' first stars)


Quantum Gravity ?

Sloth Sloth (few large steps)(few large steps) and Ant and Ant (many small steps)(many small steps) have same velocity have same velocity on flat surfaceon flat surface

On uneven ground,On uneven ground,Ant seems to beAnt seems to beslowerslower (follow structures) (follow structures)

QG couldQG could makemakespace foam-like;space foam-like;long wavelengthlong wavelengthless affectedless affected==>==>Low energy Low energy ""seem fasterseem faster

violate violate Lorentz Lorentz Invariance !Invariance !

Big Problem in Fundamental Physics:

Standard Model Particle Physics and General Relativity can not (yet) be

combined into one uniform theory

But in most extreme conditions, SM and GR predictions are inconsistent

Quantum Gravity is one group of Meta-theories that might solve the problem, but

so far no QG predictions within experimental reach ...


Quantum Gravity ?These classes of QG-theory describe justa Taylor-expansion

#c/c = +(an#E/MQG)n

==> effect can be both possibilities(lower energy photons faster or slower than higher energy ones)

[ 'mountain with tunnel': ant can go through tunnel, while sloth must climb over the mountain ==> seems slower ]


MAGIC:Mkn501 flare June 2005:

Energy dependentarrival time ???

Full unbinned analysis:-max likelihood-‘energy cost function’==> delay ~30sec/TeV

Possible reasons for delay:-acceleration at source-emission from source-transport between source and

observer(all three types would contain interesting physics)

But: why no dispersion ??????

0.25- 0.6 0.25- 0.6 TeVTeV

0.6 - 1.2 0.6 - 1.2 TeVTeV

1.2 - 10 1.2 - 10 TeVTeV

Quantum Gravity ?


Assuming energy-independent emission time,dispersion because of Quantum-Gravity effects #c/c = -#E/MQG1 or #c/c = -(#E/MQG2)2

MQG1 = (0.47+0.31-0.13) 1018 GeV ?? MQG2 = (0.61+0.49-0.14) 1011 GeV ?? [ but be careful with statistics of ‘1’ ] or 95% lower limits: MQG1 > 0.21 1018 GeV ; MQG2 > 0.27 1011 GeV much better than any other measurement [at that time] (the main constraint is not coming from the maximum time delay, but from the duration of the flare <==> limit on maximum dispersion)

Quantum Gravity ?


unexpected detection of very short AGN flaresallow to investigate unexplored physics rangebut:

Need many short flares at varying z !!!! (to distinguish source-intrinsic vs. transport effects; HESS PKS-2155 flare shows no clear time-delay)

Is analysis sensitive to short flares ????? A short flare might go undetected if source is in quiet state, because 10min flare smeared out over 2h observation .....

Apply different rules than for source detection ???

Optimal procedure to find short flares ?!

Quantum Gravity ?


Quantum Gravity ?Want to measure #t = #c * dist ~ #E * dist

Possibilities: Pulsars: #t very precise, #E rather small, dist very small

GRBs: #t rather precise, #E small, dist huge

AGNs: #t rather precise, #E large, dist large

Current results (linear term): Crab Pulsar EGRET: MQG1 > 0.2 1016GeV MAGIC: > 0.8 [2009] GRBs SWIFT: > 0.9 FERMI: >130. [2009] AGN MAGIC: > 21. (*) H.E.S.S: > 70.

(*) MAGIC Mkn501 flare by far best limit for MQG2 and higher order15.May.2009 A.Biland: Very High Energy Astronomy 214

Current StatusMany new VHE sources found,but very difficult to understand physicsprocesses....

Need extended multi-wavelength campaigns: radio + optical + X-ray + GeV + TeV ...

Extremely difficult to organize for variable objectsNot even known if variability is to be expectedsimultaneous and on same time-scale in differentE-bands/wavelenghts

Theory (model building) suffers from ‘GiGo’ effect(Garbage in ==> Garbage out)

Soon GLAST/FERMI will do full-time coverage in GeV range, but we lose most

important X-ray satellite (running out of consumables)

Other difficulty: objects interesting (=bright) in TeV usually very faint

(=uninteresting) for e.g. radio community

==> have to convince many different communities to spend large amount of

scarce observation time on (for them) uninteresting sources without any

guarantee for success !!! (many people more interested in finding 'new source'

than in 'understanding physics')

[plus: campaign must be organized well in advance, but e.g. the few IACTs might

finally be hindered by bad weather during the observation...]


Cosmic AcceleratorsDifferent classes of accelerators actingon completely different time scales:

Typical values: GRB: ~10-7 y AGN (flares): ~10-3 y SNR: ~103 y Neutron Stars: ~107 y (AGN (steady): >108 y?

(remind: CR flux ~stable since 108 y)

(probably also different energy scales ....)15.May.2009 A.Biland: Very High Energy Astronomy 216

Cosmic Accelerators

Problem:-plethora of known classes of astrophys. objects can contribute to CR

-most classes confirmed as accelerators by Cherenkov telescopes (see next week)

-different accelerators should be efficient in different energy ranges or result in different spectral indices

=> why so little structure in CR spectrum ?


Cosmic AcceleratorsProblem:What is accelerating?

But also: Why so little structure in CR spectrum ???


Dark Matter


76th Anniversary:

Fritz Zwicky, 1933: Velocity dispersion ofComa cluster indicates Dark Matter (DM) , , - 1000 km/s . M/L - 50”If this overdensity is confirmed we would arriveat the astonishing conclusion that dark matter ispresent [in Coma] with a much greater densitythan luminous matter.”

==> Evidence for DM (1) 15.May.2009 A.Biland: Very High Energy Astronomy 220

Evidence for DM (2)Measurements of rotational speedof stars in galaxies:

must exist ‘non-visible’, gravitational halo

KEPLER:Gravity / Centripetal Acceleration

!

GM

r2

=v

2

r

Data: ! ~ "onstan#

==> Evidence for DM (2)


Evidence for DM (3)Colliding galaxies (e.g. ‘bullet cluster’):- collisions of stars very unlikely- galaxies consists mainly from gas and dust==> gas heated up by friction => visible

can also measuregravitational massdistribution by weaklensing of backgroundgalaxies==>matter==mass (frictionless !!!)


majority of gravitational mass was not affected by galaxy collision ==> has no

friction, i.e. no interaction


Evidence for DM (4)


00121121= 1.02±0.02= 1.02±0.02 0033= 0.73±0.04= 0.73±0.04 00MM=0.27±0.04=0.27±0.04

( (00DMDM=0.23±0.04, =0.23±0.04, 00bb=0.044±0.004)=0.044±0.004)

Hubble constant h= HHubble constant h= H00/100km/100km-1-1ss-1-1MpcMpc-1-1 = 0.71 = 0.71+ 0.04– 0.03

! Cosmological Scales:Cosmological Scales: Cosmic Microwave Background (CMB), recent WMAP data:

CMB anisotropies " stringent constraints on cosmological parameters CMB ## large scale structure data (2dFGRS) ## Lyman 4 ## BB BB NucleosynthesisNucleosynthesis

! Galactic scale Galactic scale ## scale of galactic clusters scale of galactic clusters (rotational curves):

" Evidence is compelling, however, does not allow to determine total amount of DM in Universe

Non-baryonic DM needed for structure formationNon-baryonic DM needed for structure formation


DM information from Astro

Have no ideaabout DE;

What is DMmade of ???==>particle physics

bullet cluster

It is very simple:

the dark area between

the stars

this is the dark matter

Composition of the universe: 4% ‘barionic matter’ (SM); only small fraction luminous 23% ‘dark matter’ (DM): normal gravitation, but not SM 73% ‘dark energy’ (DE): negativ gravitation, ???


SupersymmetrySUSY: extension of 'Standard Model' (SM),invented to overcome some intrinsic problemsof the SM

In many incarnations, it predicts theexistence of a massive, stable particlehaving only weak interaction with normalmatter (plus gravity) => LSP

This particle could naturally explain DM

Lightest supersymmetric Particle (LSP)


GUTELW RGE

Supersymmetry SUSYMSUGRA Assumptions:

" Unify Higgs and scalar sector at the GUT scale" Unify all trilinear couplings at the GUT scale" Break radiatively the electroweak symmetry

Only FIVE parameters leftmo m1/2 Ao tan% sign(µ)

!

(˜ s , ˜ c )L

!

( ˜ u , ˜ d )L

!

˜ " o

!

˜ " ±1

2

34

1

2

Mass

!

˜ g

!

( ˜ u , ˜ d )R

!

(˜ s , ˜ c )R

!

h

!

H,A,H±

!

˜ t 1

!

˜ b 1

!

( ˜ b , ˜ t )2

!

˜ e R

!

˜ µ R

!

( ˜ " , ˜ e )L

!

( ˜ " , ˜ µ )L

!

( ˜ " ,#2)

L

!

˜ " 1

Schematic Particle Spectrum

LEP limits: Mass of sparticles > Ebeam tan% > 2.5

mh > 114.4 GeV m5± > 103.5 GeV m56 > 58.6 GeV


Search for SUSYa) creation at colliders: (simulation)

n leptons + n jets + missing ET

Mass reach for gluino and squark

~ 2-3 TeV

Typical event signature in CMS Detector at LHC:


Search for SUSYb) direct search: when LSP interacts with nucleus, the nucleus recoils,

hits surrounding atoms and releases energy in the

form of heat or light ( LSP = lightest SUSY particle) Interaction of LSP with ordinary matter: few events/kg/year

Main problem: background events fromdetector impurities (radioactivity) and CR~106 times higher than expect. SUSY rate

Ni = detector mass / atomic mass of nuclei species in% = % energy density / % mass (local % density)

<&i%> = scattering &, averaged over the relative % velocity w.r.t. detector

!

R " Ni

i

# n$ <%i$ >

scattering cross sections depends on SUSY parameters (several orders of

magnitude ...)


Search for SUSYmany detectors worldwidetwo main detector techniques:- Heating due to recoiling nucleus giving up its kin. energy: need cryogenic detectors (T ~ mK)

- Scintillation: excited ions produced via recoiling nucleus,e.g.

Liquid Argon Liquid Xenon

NaI

in preparation: ArDMA.Rubbia (ETH) et al. [ Lilian Kaufmann ]


Direct Searches

R. Mahapatra,Talk at DarkMatter 2008,UCLA, Feb. 2008

New CDMSresult

Xenon 10


Direct SearchesOther idea: earth moving relative to DM

==> look for yearly modulation in the signal(background and other systematics cancel?)

DAMA experiment sees strong yearly modulation

Overall motionOverall motionof solar system:of solar system:

220 220 km/skm/sEarth orbits sun

at 30km/sat 30km/s

NorthernNorthernsummersummer

NorthernNorthernwinterwinter

Net velocity: 235 Net velocity: 235 km/skm/s

Net velocity: 205 km/sNet velocity: 205 km/s

If our solar system moves If our solar system moves through a high density of through a high density of LSP gasLSP gas$$ one expects periodic one expects periodic seasonal variations seasonal variations (few %) of the signal (few %) of the signal


Direct Searches

DAMA result disagreeswith other experiments

Generally assumed thatDAMA oscillation is realNot induced by DM butby unknown yearlysystematic effect(temp., pressure, ????)

New CDMSresult

Xenon 10

DAMAdetection

???

DAMA first published in 2005

significantly improved measurement since then, effect still exists (and many

possible detector systematics (claimed to be) excluded


Search for SUSYc) indirect searches:LSP is stable ==> can not decaybut LSP is ‘Majoranaparticle’ ==> 2 LSPscan annihilate intoSM particles


Indirect Search! most interesting, because can be traced to source; but:

! only produced in higher order or secondary processes

==> rare or rather low (for IACTs) energy ?!!! production would be perfect signal (E! = LSP mass !), but extremely rare


Indirect SearchExpected flux depends on SUSY parametersand on DM-mass distribution:

Flux calculationFlux calculation:

!

" =N(#$)

4% m&2'

1

()d) *2++ ds

Particle physics CDM density distribution

look for regions with high 72

==> high gravity (low luminosity)

-Galactic Center: nearby ==> possible to measure 7(r) ?-Dwarf Galaxies: rather near, very low luminosity-Galaxy-clusters: extremely high gravity

-center of sun, center of earth: very nearby, but low gravity

CDM density distribution not well known ==> uncertainty in flux prediction by

several orders of magnitude


Indirect SearchProblems:-Galactic center: HESS/MAGIC=>other bright VHE source-Dwarf Galaxies: expected to be dim (MAGIC obs. Draco)-Galaxy clusters: too extended; other VHE sources-center sun|earth: not observable

Other possible sources:-’minihalos’: N-body simulations predict much more DM clumps than known Dwarf galaxies-Intermediate Mass Black Holes: ~104 Mo could have accreted huge amount of DM since big bang ==> extremely bright

Problem minihalos, IMBH: nothing but DM annihilation==> invisible for astro ==> don’t know where to look



Search StrategySatellites (GLAST,AGILE) discovercandidates(Unid. with veryhard spectra),

IACTs (MAGIC,HESS,VERITAS,CTA) find cutoffas smoking gun

AGILE,

GLASTMAGIC,

HESS,

VERITAS

old plot; more striking including intermed. Bremsstr.15.May.2009 A.Biland: Very High Energy Astronomy 238

Complementarity between direct detection andindirect detection through gamma-rays: Scan ofWMAP-compatible MSSM models

Present approximate limitfrom direct searches(Xenon10 and CDMSexperiments)

Approximate reach ofGLAST and IACTs (?)


Dark Matterexist many more models:

0

-10

-20

-30

log (,

int /

1pb)

-10-15 0-5 5 10 15

log (m / 1GeV)

-40 keV GeV MGUT

Schematic representation of some DM Candidates

Roszkowski, hep-ph/0404052 v1

'

Axion

Gravitino

WIM

Pzi

llas

5KK

WIMPs

WIMP = Weakly Interacting Massive Particle

!! (Standard Model) Neutrinos (Standard Model) Neutrinos

!! Sterile Neutrinos Sterile Neutrinos

!! AxionsAxions

!! Supersymmetric Supersymmetric candidates:candidates:%% NeutralionsNeutralions

%% Sneutrinos Sneutrinos

%% Gravitinos Gravitinos

%% Axinos Axinos

!! DM from Little Higgs ModelsDM from Little Higgs Models

!! Kaluza-Klein Kaluza-Klein States (ED)States (ED)

!! Superheavy Superheavy DM: DM: WIMPzillasWIMPzillas

!! •• •• •• ••

standard model neutrino as main component of DM ruled out by experiments


As in every problem in Astro-Particle Physics, we might notyet have asked to correct question; but maybe very close...

very high energy astronomy cosmic ray · called ‘2nd order fermi acceleration’ or short ‘2nd...

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