The footprint of large scale cosmic

structure on the UHECRs (and gamma) distribution

Alessandro Cuoco, Università degli studi di

Napoli Federico II

OtrantoSeptember 1 0

2006

Cuoco A, D’Abrusco R, Longo G, Miele G and Serpico P D, 2006 JCAP. 0601:009

Sky Distribution•For E>4-5 x1019 eV galactic and extragalactic magnetic fields are negligible and charged particles propagate almost rectilinearly: is it possible UHECRs astronomy?

•Energy losses impose that sources must be near (100-200 Mpc) (GZK Cutoff)

•Data from AGASA (50 events) indicate an isotropic distribution (extragalactic origin) except for a small scale clustering (point sources?)…

Energy Spectrum (2)

Cosmic-rayCosmic-rayspectrum spectrum E E2.72.7

The change in slope is generally due to a change in composition and/or The change in slope is generally due to a change in composition and/or a change in astrophysical origin or in the acceleration mechanism… a change in astrophysical origin or in the acceleration mechanism…

Unsolved problem… Unsolved problem…

The spectrum is a Piecewise Power Law:

E-γ = 2.7- 3.0- 2.8

Clearly visible the Kneeat E=1015 eV and the Ankle at E=5x1018 eV

Pierre Auger Observatory

•Auger observatory will use hybrid techniques reducing considerably the sistematics…

•Statistics of events of about 50-100 UHECRs with E>4x1019 eV per year

Southern hemisphere:

MalargüeProvincia dede Mendoza

Argentina

3000 Km2

surface

Large Scale Structures (LSS)

SDSS mesurements have confirmed the results of numerical (hydrodynamical) simulation: Universe has a foam-like Structure rich of voids and filaments along which the galaxies are aligned; The structures start to be homogeneous and isotropic by about 100 Mpc and are visible till the farest explored regions at about 1Gpc

SDSS Galaxies and Structures

1Gpc

Local Universe (200 Mpc)

2MASS Survey

Local Universe (Eq. Coordinates)

Redshift informations

IRAS PSCz Survey

Worst quality respect to 2MASS: • About 15.000 Gal. in PSCz against 1.5 millions of 2MASS, and less sky coverage, but easier to manage

• Better quality in redshifts: spectroscopic redshifts available with negligible errors

• For 2MASS only photometry is available from which photometric redshifts are calculable only with great errors (tipically 20-30%)

Mask and sky distribution of the PSCz sources

Redshift distribution and selection function

Propagation of particles

Energy Loss and Interaction Length (dE/dz)/E for a proton injected at z=0.2 and Energy=100 EeV.

Photopion Production

Bhete-Heitler Pair Production :

P + γCMB p + e+e-

Cosmological Redshift

Combined effect

Energy Loss

z

Mp

c10 E

eV

Interaction Length not always constant, expecially for photopion production due to the tight dependence of cross section on energy: exponential weight and attenuation not truly valid

Model prediction

Propagation

Can we test the hypothesis that the UHECRs come from local sources (the GZK sphere)?

Resulting Resulting UHECRs flux UHECRs flux integrated integrated from a lower from a lower threshold of threshold of 5x105x101919 eV eV

Some assumption is needed:• Sources are numerous and follow the distribution of LSS• GZK is true (quite a consequence…)• Standard propagation and particles (protons)• Magnetic fields not very strong (rectilinear propagation)

Energy Cut DependenceEcut=30 EeV Ecut=50 EeV

Ecut=70 EeV Ecut=90 EeV

Equal area Hammer–Aitoff projections of the smoothed UHECR arrival directions distribution in galactic coordinates obtained for fixed s = 2.0 and

Ecut = 3, 5, 7, 9 × 1019 eV. The smoothing angle is σ = 3◦. The contours enclose 95%, 68%, 38%, 20% of the corresponding distribution.

Method

Comparison cell by cell with a pure uniform

distribution random generated with 2 statistics:

0 50 100 150 200 250 300 350

-75

-50

-25

0

25

50

75

2

k1

Ncell #eventskmeank2meank

How many events to How many events to detect detect

the anisotropies? the anisotropies?

Forecast predictions

About 600 events required to distinguish structures froman isotropic background

Alternatives: top-down,Strong magnetic fields,

Point sources…

Dis

trib

uti

on

s n

orm

alize

d t

o U

nit

Are

a

Reduced 2: r2

2 distribution obtained from 10.000

Montecarlo simulations

AUGER proper sky coverage and exposure included:600 events about4-5 years of AUGER

200 events

400 events

600 events

800 events

Comparison of LSS model andisotropic model distributions

Power Spectrum

m

maC12

2

Strong dipole and quadrupole anisotropy!Strong dipole and quadrupole anisotropy!

Non gaussian Non gaussian features: Power features: Power

spectrum spectrum contains only contains only part of the full part of the full

map information!map information!

Magnetic Fields

In some cases strong deflections up to 50 degrees seems possible making particle astronomy not possible, but intergalactic magnetic fields are very poor known…

Worth testing!

Map of deflection Map of deflection angles from the local angles from the local

clustersclusters

Cumulative Cumulative distribution of distribution of

deflection anglesdeflection angles

From G.Sigl

Gamma Analogy

•Photon interactions at TeV energy give a gamma horizon of the same order size of GZK horizon

•The main interaction is: γγe+e-

pair production with e+e- cascading

Gamma Horizon E-z Gamma Horizon E-z PlanePlane

Critical (Critical (=1) contour=1) contour

: Optical Depth Attenuation = Exp(-

)

Stecker et al. astro-ph/0510449

Satellite and Ground based gamma ray astronomy

CANGAROO III(Australia & Japan)

Spring 20044 telescopes 10

meters ØWoomera, Australia

Windhoek, NamibiaHESS

(Germany & France)

Summer 20024 (16)

telescopes12 meters Ø

Roque delos Muchachos, Canary Islands

MAGICMAGIC(Germany, Spain, Italy)(Germany, Spain, Italy)

Summer 2003Summer 20031 telescope 17 meters 1 telescope 17 meters

ØØMontosa Canyon,Arizona

VERITAS(USA &

England)2005?

7 telescopes10 meters Ø

Air Shower Cerenkov telescopesEnergy Range > 50 GeV

GLAST: to be launched in 2007Energy Range 10 MeV-500 GeV

Wide-angle instruments surveying ~ 2-3

“Threshold” Sens. (1 y)Milagro ~ 2 TeV ~ 0.5 CrabTibet III shower array ~ 3 TeV ~ 1 CrabARGO YBJ 0.5 – 1 TeV ~ 0.5 Crab

Crab signalTibet arrayMilagro ARGO

Ground Based Surveys

Milagro Galactic Plane

• GP diffuse excess clearly visible from l=25° to l=90°• Cygnus Region at l=65°-85° and |b|<3° shows extended excess• FCygnus ~ 2 x Fcrab

Sig

nifi

can

ce

Preliminary

From B.Dingus, Elba06From B.Dingus, Elba06

Cuoco A, Hannestad S, Haugbølle T, Miele G, Serpico

PD & Tu H In Progress…

TeV Gamma SkyTeV Gamma Sky

From Large Scale Structures

TeV angular Power Spectra

Halo Model N-body Simulation

Summary and Conclusions

• In a standard scenario of composition (protons) and propagation of UHECRs GZK limits the sources to be no far than 100 Mpc (the GZK sphere)

• Anisotropies in the arrival distribution and flux of the UHECRs is expected to correlate with the local cosmological structures

• All sky astronomical surveys (2MASS, IRAS) and propagation codes can be used to construct a realistic model of the expected flux anisotropy

• Statistical analysis indicates order few hundreds events are required to distinguish the structures from isotropic background, corresponding to 4-5 years of AUGER

• Given enough statistics the model can be confirmed or ruled out: in both cases valuable conclusion: beginning of UHECRs astronomy in first case or confirmation of non standard feature in the second: strong magnetic fields, atypical sources, exotic particles and propagation…