Angela V. OlintoThe University of Chicago

Anisotropies at the Highest Energies

CMB vs UHECR Anisotropies

1. UHECRS are Charged, should ‘point’ above ~ 10 EeV Z

Halo B?

Extra-galactic B?B < nG

weak deflection

RL = kpc Z-1 (E / EeV) (B / G)-1

RL = Mpc Z-1 (E / EeV) (B / nG)-1

where EeV=1018 eV

kpc

10 kpc

strong deflection

Milky wayB ~ G

E > 1019eV

E < 1018eV

2. Cosmic RaySpectrum is Power law

Non-thermal Phenomena

Extreme Accelerators

Emax > 1020 eV

E-2.7

E-3.1

12 orders of magnitude

32 o

rder

s of

mag

nit

ud

e

RH

IC

Teva

tron

LH

C

Ankle (1 particle /km2 yr)

Ecm = PeV (Euhecr /ZeV)1/2 (2A)1/2

Swordy ‘02

3. ‘Pointing” UHECRS E ~ 100s TeV CM

ankle

knee

E = Ze B L

10% efficiency

1020eV Protons1020eV Iron

Log B(G)

Log L(cm)

others

GRBs

LHC

4. No known mechanism acceleration nor clear

Counterparts

Cosmologically Meaningful TerminationGZK CutoffGreisen, Zatsepin, Kuzmin

1966

p+cmb + p + 0

n + +

Proton Horizon~1020 eV

5. Extragalactic propagation GZK imprint

Attenuation length

e+e–

Interaction length

Attenuation length

6. GZK Effect Anisotropies

Spectral Feature

+ LSS Anisotropic Sky Distribution

Charged Particle Astronomy!!!

GZK Horizon - Protons

Allard, AO, Parizot 08

Horizons:

Gpc

1019 eV ~ 1 Gpc

1020 eV < 100 Mpc

100 Mpc

Inhomogeneous Galaxy Distribution

2MASS - Two Micron All Sky Survey

Horizons:

Gpc

1019 eV ~ 1 Gpc

1020 eV < 100 Mpc

100 Mpc

The Pierre Auger Observatoryof Ultra-High Energy Cosmic

Rays

Southern site

3 000 km2

Northern site20 000 km2

ArgentinaAustraliaBrasilBolivia*Croatia*Czech Rep.France Germany ItalyMexicoNetherlands

> 400 PhD scientists from > 70 Institutions and 18 countries

PolandPortugalSlovenia

Spain UKUSAVietnam*

*Associate Countries

18 Countries 70 Institutions, > 400 scientists

Many Candidates to win the World Cup 2010!!!

1660 tanks = 3,000 km2

Surface Array4 Fluorescence Detector SitesScience Data since 2004 Completed in June 2008

Auger South

surface detector

tanks aligned seen from Los Leones

4 Fluorescence Detector Sites

1st - 4 Fold Hybrid Event

20 May 2007 E ~ 1019 eV

Statistical 14% @ 50 EeVSystematic 22%

Less than 1 degree @ 50 EeV

> ~1 degree “astronomy” @ 50 EeV

Observed Spectrum showns GZK GZK

Unclear Trend in Observed Composition

Anisotropy Analysis

Auger Anisotropy Result 2007Highest energy cosmic rays have an anisotropic distribution!

Correlation with z < 0.018 AGNs in

the 12th Véron-Cetty/Véron catalogue

The observed correlationdid not identify the CR sources

but established anisotropy at 99% c.l.

Data: 27 events above 57 EeV from 1/1/2004 to 31/8/2007 (exposure of 8890 km2 sr y)

Auger 2007 Anisotropy ResultAuger 2007 Anisotropy Result

* - VCV AGN catalogue 3.2o- 27 highest energy event

Blue shades: equal integrated exposure

Challenges of the Analysis:

1. LOW STATISTICS!!!!!

2. Choice of catalogs

Véron-Cetty / Véron, 12th Edition, 2006

“This catalogue should not be used for any statistical analysis as it is not complete in any sense, except that it is, we hope, a complete survey of the literature.”

Significance of the anisotropy result

Not an “AGN correlation” result!1st step: search for correlations between arrival directions of

UHECR and various source catalogues

Very large “raw significance” found w/ 12th VCV catalogue of AGNs

Did not seem to be fluctuation

Auger collaboration set up a prescription for future data

Even after generous penalty factors for a posteriori searches and scanning of parameter space

(data from 2004/01/01 to 2006/05/27)

12 out of 15 events E > 56 EeV closer than 3.1° from an AGN in 12th VCV with z ≤ 0.018 (D ≤ 75 Mpc)

Most significant a posteriori “correlation signal”:

3.2 expected from isotropic distribution

Exploratory scan (Period I): 1 Jan 2004-27 May 2006Integrated exposure: 4390 km2 sr y

Scan in ψ(angular distance between CR and AGN), Eth (CR energy), zmax (AGN distance)

Scan implemented to find the minimum of the binomial probability P that ≥ k out of N events correlate by chance

Minimum value of P: Eth = 56 EeV ψ = 3.1o zmax = 0.01812/15 events correlate (3.2 expected by chance, p(z, ψ) = 0.21)

Scan proper penalization difficult to calculate Prescription adopted

p(z, ψ)= exposure-weighted chanceprobability for a CR to fall within ψ of the sources

≤ 3.1°z ≤ 0.018

(D ≤ 75 Mpc)E ≥ 56 EeV

3 Parameter Scan3 Parameter Scan

correlation is most significant above E = 56 EeV where the CR flux drops…

Energy Threshold makes senseEnergy Threshold makes sense

Significance of the anisotropy result

2nd step: predefine a region in the sky of excess CR flux & test if next UHECRs come from this region

Independent data set, prescribed parameters, unambiguous significance

21% chance from isotropic distribution

Nearby VCV AGN 21% sky

Independent data (Period II): 27/5/2006-31/8/2008Integrated exposure: 4500 km2 sr y

A-priori fixed parameters: Eth = 56 EeV ψ = 3.1o zmax = 0.018

8/13 events correlate (2.7 expected by chance)

Probability to happen by chance from an isotropic flux: P≈1.7 10-3

Test built to have 1% probability to incorrectly reject isotropy.

Test passed: 99% c.l. anisotropy

Note: it does not show that VCV AGN are UHECR sources!

First 27 events

Exploratory scan – 12/15 events correlated (3.2 expected)Prescription passed when 8/13 correlated (2.7 expected)

NOTE: original set became 14 events when reconstructed with new energy analysis, 14+13 = 27

References

Science 318 (2007), 939“Correlation of the highest energy cosmic rays with nearby extragalactic objects”

Astroparticle Physics 29 (2008), 188“Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei”

arXiv:0906.234731st International Cosmic Ray Conference, Lodz , Poland, July 2009“Astrophysical Sources of Cosmic Rays and Related Measurements with the Pierre Auger Observatory”

NEW Update to come soon...

ICRC Update 2009ICRC new data (Period III): 27/5/2006-31/3/2009after exploratory period (II+III) integrated exposure: 12650 km2sr y

Updated event reconstruction: 56 EeV 55 EeV

31 new events E > 55 EeV: 44 post-prescription events

A-priori fixed parameters: Eth = 55 EeV ψ = 3.1º zmax = 0.018

mask = cut outGalactic Plane

ICRC 2009Likelihood ratio: binomial probability of correlationover binomial probability in isotropic case (piso=0.21)

17/44 events in correlation (P=0.006)Isotropy still rejected at 99% c.l.

Time Ordered Degree of correlation (p=k/N)

pdata=17/44=0.38±0.07Correlation degree decreased wrt our previous report

but still more than 2 s.d. from isotropy

A Posteriori Analysis

Point source searches

Different methods & Catalogs (w/ ICRC 2009 Data):

I. Cross-correlationII. Log-likelihoodIII. 2-fold correlation

Laura Watson: Bayesian Methods applied to 2007 data Fred Kuehn: Methos used in the collaboration

Centaurus A

Centaurus A

KS test: 2% of isotropic realizations have a maximum departurefrom isotropy ≥ the maximum observed departure

Integral number of events vsangular distance from Cen A

Maximum excess @ 18o radius: 12 observed events vs 2.7 expected

1. X-ray AGNs in 22-months SWIFT-BAT catalogue (261 objects)

2. Galaxies in the HIPASS survey (3058 galaxies, radio, flux-limited, HI sources)

3. HIPASS-HL: sub-sample of HIPASS (the 765 most luminous galaxies)

4. Galaxies in the 2MRS compilation (|b|>10¡, 23000 most luminous galaxies from 2MASS, full-sky, IR)

Other (Better) Catalogs

Cross Correlation

e.g.: volume selected galaxies(D<200 Mpc) from 2MRS (1940 obj)

Measures the excess of pairs within a given angular separation wrt isotropy (departures are larger if CRs correlate with denser regions of the catalogues)

No weight by distance or luminosity (equal contribution to CR flux from every source)

Smoothed Maps from Catalogs For each catalogue: Smoothed probability maps of arrival directionsWeight catalogue sources by flux x GZK attenuation

2 free parameters: smoothing angle σ and isotropic background (catalogue incompleteness + lower en. spill)

Fc(n) = density map value in the direction n

Use data to find the best values of (σ, fiso) by maximizing the LogLikelihood

Parameters weakly constrained

Likelihood Test

Simulate 104 samples with the same number of data as in the real set

Draw events according to catalogue density map or isotropically

Compare the likelihood distributions with the value obtained from data

Better agreement with Catalog models vs Isotropy

LL sensitive to data points “in or out” of high density catalogue regions

Simulated data sets based on isotropy (I) and Catalog models (II) compared to data (black line/point).

Complementary method to testoverall proportionality betweenmodels and data

Based on the computation of twocoefficients: correlation (testmatch between models and data)and concentration (test clusteringproperties of data)

Data compatible with all themodels

The map based on SWIFT givesthe most discriminant test againstisotropy

2-fold correlation method

up to 3/31/2009, exposure 17,000 km2sr.y, 58 CRs w E>55 EeV

Update on the correlation with VCV objects (a-priori analysis) Isotropy rejected at 99% c.l. Degree of correlation lower than in early data

A-posteriori analysis: Excess of events close to Cen A (?) Distribution of arrival directions compatible with several catalogs that trace the distribution of nearby extra-galactic matterX-rays AGNs (e.g., SWIFT-BAT) interesting correlationsMore statistics needed to discriminate possible source scenarios

“Only” collect ≈ 2 UHECR/monthOnly look in the Southern Sky

Conclusions

Auger North 10 yr

Black – 2MASS catalog z<0.02Blue – Auger North simul Data – energy proportional to circle sizeRed – Auger South Data

50 CERN, 11 December 2007

— Particle Physics Seminar: Auger

results on UHECRs —

NEED MUCH HIGHER STATISTICS!!!!

The poorest, but very energetic!

THANKS!!!