Deflections of Ultra High Energy Cosmic Rays by Intergalactic Magnetic FieldsBased on astro-ph/0310902withKlaus Dolag (Dipartimento di Astronomia - PadovaVolker Springel (Max Planck Institute for Astrophysics - Munich)Igor Tkachev (CERN )

Ultra High Energy Cosmic RaysUHECRCosmic Rays spectrum

Why UHECRs are so interesting?Likely, they are of extra-galactic origin

The acceleration mechanism is unknown and it may involve new physics

Galactic magnetic field are not expected to deflect them significantly UHECR may point their sources if intergalactic magnetic fields are not too strong

Plan of the talkObservational situation: UHECR energy spectrum and angular distributionWhy, most likely, UHECR come from astrophysical sourcesHow far UHECR can travel; why they are nucleiGalactic and intergalactic magnetic fields and their originReconstructing the IGMF by numerical simulationsMaps of deflections and general resultsConclusions

The observational situation

Extensive Air ShowersGround Arrayseither scintillators or water cherenkov tanks are deployed on a large region.The energy of the particle is obtained by measuring the density of particlesat 600 m from the core of the shower.

FluorescenceTelescope antennas are used to detectthe isotropic 300-400 nm radiation emitted by fluorescence from the nitrogen molecules in the atmosphere.

Energy and composition are measured from the position of the maximum of theshower.

EAS experimentsTHE PRESENT:AGASA: ground detector [acceptance 160 km2 sr , angular resolution ~ 20] HiRes (monocular): fluorescence detector [350 km2 sr, angular resolution ~ 1o (binocular)]

THE FUTURE:AUGER (ground + florescence) [accep. 7000 km2 sr, res. 1.5o]

EUSO ( fluorescence from the space)[accep. 35000-70000 km2 sr]

Energy spectrum: AGASA vs HiResAGASA ~ 900 events with E > 1019 eV~ 100 4 1019 eV~ 15 1020 eVHiRes 2 events with E > 1020 eV (expected 20 by assuming AGASA flux)

Energy spectrum: AGASA vs HiRes - discrepancy reduces at ~ 2 between the two experiments - AGASA is compatible with the GZK cut-off at 2.3 Hopefully this will be settled by AUGER which combine both techniques ! By correcting for possible systematic in the energy determination - 15 %+ 15 %Blasi, De Marco & Olinto 03

The composition of UHECR From the study of EAS development

Haverah Park [Ave et al. 2001]No more than 48% of the inclined showers can be photons above 1019 eVNo more than 54% can be Iron above 1019 eVNo more than 50% of the showers can be photons above 4 1019 eVNeutrinos are excluded (if the cross section is not enhanced)Fly's Eye [Dawson et al. 98]Transition from heavy (at 1017.5 eV) to light composition (at ~1019 eV)Similar limits from AGASA

Angular distributionGalactic planeSupergalactic planeDoublets and triplets Flys Eye + AGASA: excess of events (4 %) for 0.4 < E < 1.0 1018 eV in the direction of the galactic center For E > 4 1019 eV AGASA and HIRes find no evidence of a large scale anisotropy UHECR must be extragalactic or be produced in an extended halo !! No evidence of an excess along the supergalactic plane

The Local Super Cluster (LSC)~ 40 Mpc~ 10 Mpc

How far UHECRs may come from ?The GZK cut-off and the composition of UHECR

PROTONS

Energy losses due to

The GZK cut-off AGASA ONLY !! may be due to a systematics or to a local excess of sources (top-down models) orTo a local confinement of UHECRs due to strong magnetic fields in the LSC

NEUTRONSThey decay after travelling a distanceCOMPOSITE NUCLEI(Less interesting in this context since they smaller Larmor radius)

Same energy losses as for the proton + photodisintegration

At 1020 eV they cannot travel more than ~ 10 Mpc

PHOTONS(electromagnetic showers)Protheroe & Johnson 96(NO MAGNETIC FIELDS)

The large scale isotropy is not a problem for protons For E 5 1019 eV lE 1 Gpc The flux is dominated by far source No expected excess along the Supergalatic plane !

The some doesnt hold for photons since lE() < 10 MpcA large component of UHECRs is composed by protons or nuclei

Why UHECR sources are astrophysical:The spectrum of CR is practically a single power law

There are evidence for small scale clustering

Hints for a correlation between UHECR and BL-Lacs

Small scale clusteringAGASA: 92 events with E > 41019 eV - 8 doublets - 2 triplets

Chance probability to reproduce them with a homogeneous distribution of sources:

Pchance < 1 %AGASA + Yakutsk [Tiniakov & Tkachev, 01] Pchance < 10 -5 (different treatment of triplets) SIGNIFICANT INDICATION THAT SOURCES MAY BE POINT LIKE

The BL-Lacs - UHECR connectionChance probability to reproduce that with uniform sources P < 10-4From a sample of 22 BL-Lacs 5 coincide with UHECR arr.dir. Crossing BL-Lacs catalogue with EGRET sources gives 12 BL-Lacs4 UHECR source candidates are among these 12 !The remaining 10 correlate with UHECR after correcting for the galactic field ( if Q = + 1). Gobunov et al. astro-ph/0204360

Tinyakov & Tkachev astro-ph/0102476

Galactic and intergalactic magnetic fieldsObservations

Galactic magnetic field

Nuclei Deflections in the Milky Way the regular field give rise to undetectable deflections at 1020 eV the galactic disk signature should be visible if sources are galactic and UHECR are not heavy nuclei Sizeable deflections at 1019 eV which, however, can be disentangled ![See e.g. Tinyakov & Tkachev 03]

The random field produce ~ 1 o deflections

Magnetic fields in galaxy clustersComa cl. : visibleX-raysradioSynchrotron emission

X-ray non-thermal emissions

Faraday Rotation Measurments (RMs)Coma RMs

MF in the Inter-Galactic Medium (IGM)Only upper limits are available based on the Faraday Rotation Measurements of Quasars radio emission at cosmological distance (z ~ 1)LCFirst limit by Kronberg94 who, however assumed ne = const. and b = 1 !! Then Blasi, Burles and Olinto, `99 accounted for ne inhomogen. in Ly-alpha clouds UHECR deflections may be large if these limits are saturated !

Possible origin of magnetic fieldsPrimordial seed + dynamo amplification in galaxies + pollution of the IGM by galactic winds

Ejection from AGNs + amplification during the cluster accrection

Battery + amplification during the cluster accrection

Primordial origin ( phase transitions in the early universe, generation at neutrino decoupling, the inflation) + amplification during the cluster accrection [For a review see D.G. & Rubinstein 01]

MHD SIMULATIONS FAVOUR 2-4

MSPH simulations in galaxy clustersN-body simulations of DM + gas hydrodynamics (SPH) + MHD MSPH: Magnetic Smooth Particle Hydrodynamics[Dolag, Bartelmann & Lesch, astro-ph/0109541, 0202272].gas particle + magnetic fieldDM particleThe initial DM fluctuations are fixed at z = 20 compatibly with CDM Smoothing length

Magnetic field evolutionThe MF is evolved starting from a seed (AGNs, battery or primordial) The electric conductivity of the IGM is practically infinite

The magnetic field is amplified by: ADIABATIC COMPRESSION:MHD amplification by shear flows:The memory of the initial power spectrum is erased !

Simulated RMsRMs profile is reproduced for

Reconstructing the magnetic structureof the local universe Basic assumption: magnetic fields in galaxy clusters are originated by a uniform primordial seed generated at high redshift

Motivations: - this is easier to be implemented numerically - it should give the largest deflections of UHECRs Approach: - we combine MSPH simulations previously performed for galaxy clusters with constrained simulations of the local universe LSS

Simulations of IGMF in the local universeWe need a realistic 3D simulation of the LSS such that the size and position of simulated structures (clusters) coincide with those observed on the sky. We need to know the observer position in the magnetized structure.

The size of the simulation volume has to be > 50 Mpc such to enclose the Local Super Cluster (LSC) the GZK sphere REQUIREMENTS

Constrained simulationsInitial conditions (density fluctuations) are chosen randomly from a Gaussian field with a power spectrum compatible with CMD cosmology but constrained so that the smoothed density field coincide with that observed.

Simulations of this kind have been performed, successfully, to simulate the local flow [Mathis, Springel, White et al. , astro-ph/0111099]

OUR SIMULATIONSimulation volume: 80/h Mpc = 107/h70 Mpc gas mass resolution 5 x 108 Msun ; max spatial resolution ~ 10 kpcInitial redshift: z = 60Initial magnetic field: B0 = 1 x 10 -11 G lC = CONSTRAINED SIMULATION OF DM AND GAS + MSPHWe use IRAS 1.2 galaxy catalogue to constrain initial conditions

Results of the MHD simulationCLUSTERS: Bc = 1 - 10 G - OK with RMs - LC

RAY TRACINGWe sum deflections produced by every gas particle If > 5 o trajectories are ignored Proton energy: E = 4 1019 eV Energy losses can be neglected up to ~ 1 Gpc ( deflections at larger energies can only be smaller !! )Smoothed gas particle

Deflections up to 107 Mpc

What we learn from these maps ? UHECR cannot be isotropized !!Large deflections are produced only in gal. clusters which cover only a tiny fraction of the skyFilaments produce small deflections (< 2o) At large distances the bulk of deflections is due to filamentsNo observable deflections in the local region and in the voids

Sky fraction covered by observable deflections Self-similarity is consistent with a uniform density of deflectors (filaments)For d a large number of filaments is crossed, each time giving a random 0.5 There is a considerable fraction of the sky where correlation with source is preserved !! OK with small scale clustering and UHECR-BL Lacs correlation

The effect of a possible unclustered fieldObservable only if lC > 20 Mpc

Quite hard to get unless the field is primordial and generated during the inflation

To be expected only if the field is of primordial origin

ConclusionsWe performed the first simulation of the magnetic structure in the local universe The simulation reproduce MF observed in galaxy clusters and give new hints on the MF in less dense regions like filamentsAccording to our results the LSC is weakly magnetizedUHE protons undergoes large deflections only when they pass trough clusters and ~ 1o deflections in filamentsOur results are compatible with small scale clustering and UHECR-BL Lacs correlation

CHARGE PARTICLE ASTRONOMY SHOULD BE POSSIBLE

Auger like Haverah Park use water tank (Cerenkov)Flys Eye is in agremment with recalibrated Haverah Park . We will discuss about the origin of these fields