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Search for the Ultra High Energy Cosmic Ray Sources : the Current Status Hang Bae Kim (HanYang University) High1-2014 KIAS-NCTS Joint Workshop on Particle Physics, String Theory and Cosmology February 12, 2014

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Ultra-High-Energy Cosmic Rays 1 particle/km 2 /century Ultra-High Energy Cosmic Ray (UHECR) Energy : 1962, E>10 20 eV at Vocano Ranch 1991, E=3 £ 10 20 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 energies? Cosmic Rays High energy particle from outer space Primarily composed of proton & nuclei Originated from SNe, AGN, … ? Influence on the life

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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 / scintillator Composition Energy Arrival Direction

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Observation Detection of EAS Surface Detector (SD) – e, ¹ Fluorescence Detector (FD) - UVL Cherenkov Radiation Radio wave Radar reflection Longitudinal development Lateral distribution

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Pierre Auger Observatory (PAO) Fluorescence Detector – PMT Location : Mendoza, Argentina SD : 1600 water Cherenkov detector, 1.5 km spacing, 3000 km 2 FD : 24 telescopes in 4 stations 60 km Surface Detector – Water Cherenkov

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Telescope Array (TA) Surface Detector – Plastic Scintillation Fluorescence Detector – PMT 35km SD array FD station MD LR BRM Location : Utah, USA SD : 507 plastic scintillation detector, 1.2 km spacing, 678 km 2 FD : 18 telescopes in 3 stations

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JEM-EUSO (planned)

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Signal & Timing Lateral distribution S(1000) Good energy estimator Distance from the shower axis Energy, Arrival Direction Fluorescence Detector Surface Detector Longitudinal development Energy Calibration through hybrid events Energy Calibration through hybrid events

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Composition Longitudinal development X max, the depth of shower maximum depends on energy and composition of primary CR particle. atmospheric depth Shower maximum X max, depth of shower maximum Observed variation of X max as a function of energy. Average longitudinal development of proton and Fe nucleus obtained from simulation. Proton has larger X_{max} than Fe.

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Propagation Energy Loss UHECR p, A, γ interact with CMB photons. The energy of protons as a function of the propagation distance. Modification factor of energy spectrum Injected spectrum ! Observed spectrum

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Propagation Deflection Magnetic fields ! Deflection and Time lag Galactic magnetic field B G ~ 10 -6 G R G ~10 kpc Extragalactic magnetic field B EG ~ 10 -9 – 10 -6 G (very uncertain) Proton propagation in a magnetic field of 10 -9 G

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Production Top-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 dominant Arrival Directions – Galactic anisotropy

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Production Bottom-up : Acceleration of charged particle at astrophysical sites Maximum attainable energy Acceleration mechanism Diffusive shock acceleration Acceleration site AGN, GRB, …

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Latest Results and Issues Energy spectrum 1990s, AGASA reported No GZK cutoff. HiRes, Auger, TA confirmed GZK cutoff. Abu-Zayyad et al. (2013)

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Latest Results and Issues Composition 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)

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Latest Results and Issues Arrival 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

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Study of Arrival Directions Experiment Modeling Observed AD distribution Expected AD distribution Statistical Comparison Probability that the observed distribution is obtained from the expected distribution Test Methods - Statistic Multipole moments, 2D KS, … KS on the reduced 1D distribution Test Methods - Statistic Multipole moments, 2D KS, … KS on the reduced 1D distribution Isotropy Astrophysical Objects Isotropy Astrophysical Objects Simulation

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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.

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Kolmogorov-Smirnov Test Comparison of two one-dimensional distributions Kolmogorov-Smirnov statistic Cumulative probability distribution KS statistic Probability that the observed distribution is obtained from the expected distribution Kuiper statistic Anderson-Darling statistic

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RA, DEC Distribution 2D Distribution 1D Distribution Observed Data (TA, E≥1 EeV ) Simulation Data (Isotropic) RA Distribution DEC Distribution

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Auto-Angular Distance Distr. (AADD) clusteredisotropic Caution: AADD is not an independent sampling. Probability(D) must be obtained from simulation.

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Correl. Angular Distance Distr. (CADD) correlatedisotropic H.B.K, J. Kim, JCAP 1103, 006 (2011)

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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

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Super-Heavy Dark Matter (SHDM) Model Unfavorable

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AGN Model Hypothesis : UHECRs are composed of AGN contribution, fraction f A Background (isotropic) contribution, fraction 1-f A Selection of UHECR data Energy cut We take Selection of AGN Distance cut We take Notes The fraction f depends on E c and d c. PAO-AGN H.B.K, J. Kim, JCAP 1103, 006 (2011) IJMPD 22, 1350045 (2013)

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UHECR flux from AGN For simplicity, we assume the universality of AGN. Expected flux AGN contribution fraction f A, Isotropic component fraction 1-f A, AGN Model UHECR Luminosity Distance Smearing

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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 distribution. PAO data are not consistent either with the hypothesis that they are completely from AGNs. Adding isotropic component can make the consistency improved.

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Consistent with the simple AGN model when enough isotropic component is added. Cf. Fiducial value of f AGN Model PAO

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Point-wise Anisotropy Idea – Sweep the whole sky and perform the point- wise comparison to the isotropic distribution (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.K MPLA 28, 1350075 (2013)

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

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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 background the Cen A fraction the smearing angle M87 Centaurus A The PAO data show the clustering of UHECRs around Centaurus A.

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Cen A as a UHECR source Among 69 UHECR observed by PAO, about 10 (6 ~ 17) UHECR can be attributed to Cen A contribution.

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Cen A as a UHECR source Incorporation of Void structure H.B.K, JKPS 62, 708 (2013)

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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

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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 model for Z=1 (proton). The Galactic plane section of the disk field of the PS model

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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 detected at the earth, and black bullets connected by yellow lines mark the arrival directions before UHECR enter the GMF.The blue square marks the direction of Centaurus A. If all UHECRs are protons, the clustering around Centaurus A is not 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)

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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 arrival 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?

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New Window to the sky Galileo’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

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