Search for the U ltra H igh E nergy C osmic R ay Sources : the Current S tatus

Search for theUltra High Energy Cosmic

RaySources : the Current

StatusHang Bae Kim (HanYang University)

High1-2014 KIAS-NCTS Joint Workshop on Particle Physics, String Theory and Cosmol-

ogyFebruary 12, 2014

Ultra-High-Energy Cosmic Rays

1 particle/km2/century

Ultra-High Energy Cosmic Ray (UHECR)

Energy :1962, E>1020 eV at Vocano Ranch1991, E=3£1020 eV at Fly’s eye(OMG particle) ~ kinetic energy of a baseball with a speed of 100 km/h

Extensive Air Shower (EAS) Extragalactic origin

Where and How can particles reach such extremely high ener-gies?

Cosmic Rays High energy particle from outer space Primarily composed of proton & nuclei Originated from SNe, AGN, … ? Influence on the life

Production

Propagation

Observation

• Acceleration of charged particles• Decay of superheavy particles

Cosmic background(Microwave, Radio wave, Magnetic fields)

• Energy loss• Secondary CR production• Deflection and Time lag

Atmosphere as calorimeter / scintilla-tor• Composition• Energy• Arrival Direction

Observation

Detection of EAS• Surface Detector (SD) – e, ¹• Fluorescence Detector (FD) -

UVL• Cherenkov Radiation• Radio wave• Radar reflection

Longitudinal development Lateral distribution

Pierre Auger Observatory (PAO)

Fluorescence Detector – PMT

Location : Mendoza, Argentina SD : 1600 water Cherenkov detector,

1.5 km spacing, 3000 km2

FD : 24 telescopes in 4 stations

60 k

m

Surface Detector – Water Cherenkov

Telescope Array (TA)Surface Detector – Plastic Scintillation

Fluorescence Detector – PMT

35km

SD array

FD stationMD

LRBRM

Location : Utah, USA SD : 507 plastic scintillation detector,

1.2 km spacing, 678 km2

FD : 18 telescopes in 3 stations

JEM-EUSO (planned)

Signal & Timing

Lateral distribution

S(1000)

Good energy estima-tor

Distance from the shower axis

Energy, Arrival Direction

Fluorescence Detector

Surface Detector

Longitudinal development

Energy Calibrationthrough hybrid events

CompositionLongitudinal development

Xmax, the depth of shower maximum depends on en-ergy and composition of primary CR particle.

atmospheric depth

Shower maximumXmax, depth of shower maxi-mum

Observed variation of Xmax as a function of en-ergy.

Average longitudinal develop-ment of proton and Fe nucleus obtained from simulation.Proton has larger X_{max} than Fe.

PropagationEnergy Loss UHECR p, A, γ interact with CMB photons.

The energy of protons as a func-tion of the propagation distance. Modification factor of energy spectrum

Injected spectrum ! Observed spectrum

PropagationDeflection Magnetic fields ! Deflection and Time lag

Galactic magnetic fieldBG ~ 10-6 GRG~10 kpc

Extragalactic magnetic fieldBEG ~ 10-9 – 10-6 G (very uncertain)

Proton propagation in a magnetic field of 10-9G

ProductionTop-down : Decay of superheavy particles, Emission from Topological defects

Superheavy particle with long lifetime Emission from topological defects Cosmic origin involves

new (cosmology + particle physics)

Signatures of top-down models• Spectral shape

– No GZK cutoff, flat spectrum• Composition

– Neutrinos and photons are domi-nant

• Arrival Directions– Galactic anisotropy

ProductionBottom-up : Acceleration of charged particle at astrophysical sites

Maximum attainable energy Acceleration mechanism Diffusive shock accelerationAcceleration site AGN, GRB, …

Latest Results and IssuesEnergy spectrum

1990s, AGASA reported No GZK cutoff.

HiRes, Auger, TA con-firmed GZK cutoff.

Abu-Zayyad et al. (2013)

Latest Results and IssuesComposition

PAO : Transition from proton to heavy nuclei- Ad hoc composition model (p, He, N, Fe)

HiRes & TA : Proton

HiRes (Abbasi et al. 2010)

PAO (Abraham et al. 2010)TA (Tameda et al. 2011)

Latest Results and IssuesArrival directions

AGASA - Isotropy with small clustering

Auger Anisotropy Correlation with AGNs

AGASA (Hayashida et al. 2000) HiRes (Abbasi et al. 2008)

PAO (Abreu et al. 2010)

TA (Abu-Zayyad et al. 2012)

PAO – Correlation with AGN• Low (<10^{19} eV) energy isotropy• Above GZK cutoff, anisotropy confirmed

Study of Arrival Directions

Experiment Modeling

Observed AD distribution Expected AD distribution

Statistical Comparison

Probability that the observed distribution is ob-tained from the expected distribution

Test Methods - Statistic• Multipole moments, 2D KS, …• KS on the reduced 1D distribution

• Isotropy• Astrophysical Objects

Simulation

Exposure Function• The detector array does not cover the sky uniformly and we must

consider its efficiency as a function of the arrival direction.• Here we consider only the geometrical efficiency.

Kolmogorov-Smirnov TestComparison of two one-dimensional distributions• Kolmogorov-Smirnov statistic

Cumulative probability distribution

KS statistic

• Probability that the observed distribution isobtained from the expected distribution

Kuiper statisticAnderson-Darling statis-tic

RA, DEC Distribution2D Distribution

1D Distribution

Observed Data (TA, E≥1 EeV) Simulation Data (Isotropic)

RA Distribution DEC Distribution

Auto-Angular Distance Distr. (AADD)

clustered isotropic

Caution: AADD is not an independent sampling.Probability(D) must be obtained from simulation.

Correl. Angular Distance Distr. (CADD)

correlated isotropic

H.B.K, J. Kim, JCAP 1103, 006 (2011)

Super-Heavy Dark Matter (SHDM) Model

• UHECR flux is obtained by the line-of-sight integration of the UHECR luminosity function L(R), which is proportional to the DM density ρ(R).

• Galactic DM contribution / Extragalactic DM contribution

• Galactic DM contribution

UHECR Luminosity

Dark Matter Profile

Super-Heavy Dark Matter (SHDM) Model

Unfavorable

AGN ModelHypothesis : UHECRs are composed of

• AGN contribution,fraction fA

• Background (isotropic) contribution,fraction 1-fA

Selection of UHECR data• Energy cut • We take

Selection of AGN• Distance cut• We take

Notes• The fraction f depends on Ec and dc.

PAO-AGN

H.B.K, J. Kim, JCAP 1103, 006 (2011)IJMPD 22, 1350045 (2013)

UHECR flux from AGN

For simplicity, we assume the universality of AGN.

Expected flux• AGN contribution

fraction fA,• Isotropic component

fraction 1-fA,

AGN Model

UHECR Luminos-ity

Dis-tance

Smear-ing

AGN Model

The cumulative probability distribution of CADD using the AGN reference set

Steep rise of CPD near µ=0 means the strong correlation at small angles.

PAO data are not consistent with isotropy, meaning that they are much more correlated with AGNs than isotropic distri-bution.

PAO data are not consistent ei-ther with the hypothesis that they are completely from AGNs.

Adding isotropic component can make the consistency im-proved.

Consistent with the simple AGN model when enough isotropic component is added.

Cf. Fiducial value of f

AGN ModelPAO

Point-wise Anisotropy Idea – Sweep the whole sky and perform the

point-wise comparison to the isotropic distribu-tion (Comparison method: CADD with a point reference)

Features of PAO AD anisotropy• One prominent excess region around Centaurus A• One void region near the south pole

Excess

Deficit

H.B.KMPLA 28, 1350075 (2013)

Features of TA AD anisotropy• No prominent excess region• Broad hot spot• One void region near the north pole

Hot spot ?

Cen A as a UHECR source Centaurus A is a nearby strong source of radio waves to γ-rays.

Modeling Centaurus A as a point source of UHECRs

H.B.K, ApJ 764, 121 (2013)

Centaurus A contribution + Isotropic backgroundthe Cen A fractionthe smearing angle

M87

Centaurus A

The PAO data show the cluster-ing of UHECRs around Centaurus A.

Cen A as a UHECR source

Among 69 UHECR observed by PAO,about 10 (6 ~ 17) UHECR can be attrib-uted to Cen A contribution.

Cen A as a UHECR source Incorporation of Void structure

H.B.K, JKPS 62, 708 (2013)

Centaurus A – a UHECR source

Estimate of intergalactic magnetic fields from the deflection angles

By using UHECRs around Centaurus A, the estimate of IGMF is

• Without voids – 10 UHECRs • With voids – 18 UHECRs

Composition and GMF Influence

Lorentz force equation

GMF model – Prouza-Smida (2003) model• Fit to observed Faraday rotations• Disk field• Toroidal field• Poloidal field

The deflection map of UHECR in the PS modelfor Z=1 (proton).

The Galactic plane sectionof the disk field of the PS model

Composition and GMF Influence

The deflections of arrival directions of 69 UHECRs detected by the PAO, due to the GMF, computed using the PS model, when UHECRs are protons (Left), or iron nuclei (Right). Red circles mark the arrival directions de-tected at the earth, and black bullets connected by yellow lines mark the arrival directions before UHECR en-ter the GMF .The blue square marks the direction of Centaurus A.

If all UHECRs are protons, the clustering around Centaurus A isnot altered significantly.

If all UHECRs are iron nuclei, the clustering around Centaurus A may be a fake due to the GMF.

H.B.K, JKPS 63, 135 (2013)

Summary• After 100 years of research, the origin of cosmic rays is still an

open question, with a degree of uncertainty increasing with energy.

• Statistically meaningful data have been accumulated, but not yet conclusive about composition and arrival directions.

• Statistical methods to compare two distributions of UHECR ar-rival directions.

– 2D → 1D reduction : CADD– KS or KP test

• Point-wise anisotropy and point source search• Centaurus A seems to be a strong source of UHECRs.

– Estimate of IGMF : – The influence of GMF may tell something about composition.– Beginning of cosmic ray astronomy?

New Window to the skyGalileo’s telescope

Jansky’s radio antenna

Penzias & Wilson’s antenna

Planck satellite

Tycho’s Mural quadrant Herschel’s telescope Hubble’s telescope

Hubble Space Telescope

Chandra X-ray telescope