Anisotropy studies with the Pierre Auger Observatory Carla Macolino 1 for the Pierre Auger Collaboration 2 Full author list: http://www.auger.org/archive/authors_2011_05.html 1 Lab. de Physique Nucleaire et des Hautes Energies (LPNHE) CNRS-IN2P3 and Universités Paris VI et VII - Paris (FRANCE) 2 Observatorio Pierre Auger, Av. San Martin Norte 304, (5613) Malargue (Mendoza) ARGENTINA
Outline The Pierre Auger Observatory The Auger observables The Auger hybrid concept Origin of ultra-high energy cosmic rays Large scale anisotropy results Correlation with VCV-AGNs Correlation with Cen A Search for multiplets Search for neutron point sources Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 2 / 18
The Pierre Auger Observatory (southern site) $)#*#+*,'-$./%,0* )$)#*#+*,'-$./%,0* Latitude 35 S Longitude 69 W 1400m a.s.l. X 870 g cm 2 Area of 3000 Km2 Data taking since 2004 Installation completed in 2008 ~ 60 km Fluorescence detectors 4 building with 6 telescopes each Telescope f.o.v. 30 30 Carla Macolino (LPNHE-Paris) Surface detectors 1680 Cherenkov stations 1.5 Km spaced on a hexagonal grid Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 3 / 18
The Pierre Auger Observatory The Auger Observables Surface Detector Surface Detector - Lateral distribution of particles - Lateral distribution of particles - 0% duty cycle - 0% duty cycle I. Composition (PRL accepted, arxiv:02.0699)! Hybrid data! Use fluorescence air shower profile - X max Air shower measurements Fluorescence Detector Fluorescence Detector - Longitudinal development - Longitudinal development - % duty cycle - % duty cycle ] 2 Atmospheric depth [gcm 0 500 Los Leones Los Morados 0 20 16 14 12 8 Height [km] σ Xmax < 20 g/c sys 15 g/c X max 6 00 Signal [VEM] 4 3 2 Signal [VEM] 4 3 2 S(00 m)! 2 / NDoF: 16.769/ 16! 2 / NDoF: 6.833/ 7 1500 E4 cal = dx de dx X max composition σ E /E 8% sys 22 % 0 2 de/dx [PeV/(g/cm ) 2 50 40 30 20 1 500 00 1500 2000 2500 1 S 00 E surface = f (S 00, θ) r [m] 500 00 1500 2000 2500 3000 r [m] 400 600 0 20 30 40 50 60 2 de/dx [PeV/(gcm )] Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 4 / 18
The Auger Hybrid Concept Angle Shower plane Fly's Eye with activated phototubes Cerenkov tanks Impact point Auger hybrid nature advantages FD calibrates Energy SD energy cross-check of hybrid and SD directions SD cross-checks FD trigger efficiency Accurate measurement of energy and direction Measurement of mass in a complementary way Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 5 / 18
Origin of ultra-high energy cosmic rays Arrival Directions The study of the arrival directions is crucial for the study of the origin of UHECRs Produced by the astrophysical sources Extragalactic origin since not deflected by GMF GZK - dicreteness of the sources the arrival directions reflect the distribution of the sources - Search for small scale anisotropies - Search for correlations between arrival directions and the positions of astrophysical objects At lower energies (EeV scale) a dipolar large scale anisotropy is expected transition galactic/extragalactic at the ankle ankle due to e ± pair production of protons with the photons of the CMB Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 6 / 18
Large scale anisotropy Large scale anisotropy expected around 1 EeV: gal/extragal transition: escape from the Galaxy as seen from the Earth effect due to the Earth motion w.r.t. CR rest frame (CMB) Search for a modulation in the first harmonic of the CR right ascension distribution: 2 different methods 1) Rayleigh analysis (for E>1 EeV): a = 2 N N i=1 b = 2 N N i=1 cos (α i ) N cell (α 0 i ) sin (α i ) N cell (α 0 i ) Amplitude and phase of the dipolar modulation r = a 2 + b 2, φ = arctan(b/a) Control of dipolar modulations of experimental origin: - Exposure modulation - Energy correction due to weather effects Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 7 / 18
Large scale anisotropy Analysis at the solar frequency for E> 1 EeV: Energy and exposure correction: 1% close to statistical noise Good control of the systematical effects 2) East-West method (for E<1 EeV weather effects are larger) see astro-ph/16.2881: I E (α 0 ) I W (α 0 ) = N 2 sin (θ) 2π π cos (θ) r sin (α0 φ) a EW = 2 N N i=1 cos (α0 i + ξ i ) b EW = 2 N N i=1 sin (α0 i + ξ i ) Amplitude and phase of the dipolar modulation r = a 2 EW + bew 2, φ EW = arctan(b EW /a EW ) + 90 π cos (δ) 2 sin (θ) Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 8 / 18
Large scale anisotropy Differential: Large scale anisotropy: sidereal frequency Energy bin: log (E) = 0.3 E<8 EeV: above energy resolution E>8 EeV: stat. to detect signal at 2% level ( 5000 events) Probability to arise such amplitude from an isotropic distribution = 45% Cumulative: No further evidence Astropart. Phys. 34 (2011) H. Lyberis at ICRC 2011 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 9 / 18
Large scale anisotropy Upper limits Measurement amplitude depending on: Latitude of the experiment Range of zenith angles d r cos δ A/S:drift motion due to regural field Gal:diffuse motion due to turbulent field C-G XCal:motion of the Galaxy w.r.t. the CMB frame (frame of extra-gal. isotropy) Phase: Does not follow a random distribution Smooth transition from 270 to 0 Likelihood test P chance = 3 Astropart. Phys. 34 (2011) H. Lyberis at ICRC 2011 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 / 18
Correlations with VCV-AGNs Correlation with the AGNs from the 12th edition of the Véron and Véron-Cetty catalogue Update of the correlation signal - up to June 2011 blue circles = AGN position within 3.1 black circles = CR event position 28/84 events correlate (33 ± 5)% correlation vs. 21% expected from isotropy P=0.006 while TELESCOPE ARRAY: 8/20-40% with 24% expected from isotropy ICRC 2009 and Astropart. Phys. 34 (20) 314 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 11 / 18
Correlation with Cen A High energy Centaurus A (NGC 5128) excess updated to June 2011 x=fraction of the sky covered by window ψ weighted by the Observatory s exposure N iso =N tot x Most significant excess was in a 18 window, now in a 24 window 19/84 events with 7.6 expected by chance correlation KS test yields P iso = 4% but significance for the excess region can only be established with independent data Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Astropart. ObservatoryPhys. 34 TAUP (20) 05.09.2011 12 / 18
Search for multiplets Search for energy-position correlated multiplets for E > 20 EeV Require events: Be aligned in the sky Have a high value of the correlation coefficient C between θ and 1/E C(u, 1/E) = Cov(u,1/E) Var(u)Var(1/E) with C(u, 1/E) > C min = 0.9 and smallest value of w one 12-plet and 2 independent -plets Chance probability from an isotropic distribution to obtain at least a 12-plet is 6% Derived density of source 4 M. De Domenico ICRC 2011 No significant evidence for the presence of correlated multiplets G. Golup ICRC 2011 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 13 / 18
Search for neutron point sources EeV neutron search possible as the mean decay lenght is λ n = (9.2 E)kpc If galactic/extragalactic transition happens at the ankle then sources inside our Galaxy accelaratng above 1 EeV Production of neutrons from interactions of CRs with hadronic/radiations background Measured gamma ray fluxes (>1 ev/cm 2 /s) could motivate this search Emission rate of neutrons > that of γ-rays of hadronic origin SD more sensitive to neutrons than γ-rays Search for point-like excesses Two analyses: 1 Blind search all over the observed sky - No excess found Upper limits on neutron flux 2 Stacking analysis on sets of strong gamma-ray emitters Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 14 / 18
Search for neutron point sources No candidate comes out above the expected distribution of the Li & Ma significances Upper limits for different energy ranges Galactic center ( 1 EeV): F < 0.007 Km 2 yr 1 Along the Galactic plane: 1 2 EeV: F < 0.017 Km 2 yr 1 2 3 EeV: F < 0.0 Km 2 yr 1 1 EeV: F < 0.019 Km 2 yr 1 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 15 / 18
Search for neutron point sources Selection of sources: Search for excesses in the direction of bright γ-ray sources Fermi LAT (0 MeV-0 GeV) and H.E.S.S. (0 GeV-0 TeV) Pulsars, PWN and SNR S stacked = (N obs N exp)/ N exp portion of the Galactic Plane covered by the f.o.v. of the Observatory distance < 9 kpc (λn at 1 EeV) brightest sources (in flux at Earth) No excess is found B. Rouillé d Orfeuil ICRC 2011 Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 16 / 18
Conclusions The Pierre Auger experiment is complete since 2008 and it is taking data since 2004 Very robust hybrid technique to detect CRs at the highest energies Many interesting results about Cosmic Ray Anisotropy: Large scale anisotropy: Most stringent upper limits at present on the amplitudes Phase does not follow a random distribution With higher statistics the galactic/extragalactic transition will be stablished Correlation with VCV-AGNs: Correlation degree stabilizing Excess in the Cen A region Search for multiplets: No significant evidence of correlated multiplets Search for neutron point-sources: No excess found in blind search nor in stacked analyses for γ-ray emitters Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 17 / 18
Thanks Thank you for your attention and have a nice TAUP conference! Carla Macolino (LPNHE-Paris) Anisotropy with the Pierre Auger Observatory TAUP 05.09.2011 18 / 18