La nascita della astronomia dei raggi cosmici? Indicazioni dall' Osservatorio P. Auger

La nascita della astronomia dei raggi cosmici?Indicazioni dall' Osservatorio P. Auger

Aurelio F. Grillo Teramo 8/05/08

Nuclear (p, He.... Fe) component

Knee

Ankle?

Few/km sqper century

pp?

Nuclei

E ZB Dacc

for extragalactic protons

On CMBR photons

EE

≈m

E

≈6 Mpc Dmax≈50−100 Mpc

The Auger hybrid concept

Almost completely operating, now 1 year full observatory !~

Fluorescence light

Fluorescence Detector FD Surface Detector SD

The Auger hybrid concept

The spectrum: most statistically significant from SD calibrated in energy by “hybrid” events - energy systematic error ~22 %, mostly from systematic of the FD detector (fluorescence yield, atmospheric transparency....)

Surface Detector SD

Fluorescence Detector FD

Ultra High Energy CR spectrum ICRC07

6

E−2.6

Evidence for GZK cutoff? Likely

fit

Cosmic Ray astronomy?

If UHECRs origin is astrophysical, astronomy may be possible above some x 1019 eV if particles are protons(and IG magnetic fields small)


Around ~1020 eV particles can only arrive fromwithin ~ 100 Mpc (in case of GZK)



Around ~1020 eV particles can only arrive fromwithin ~ 100 Mpc (in case of GZK)

A statistically significant correlation with sources in theGZK spere would unambiguously prove the reality ofthe cutoff (and give hints on the nature of sources)


The “Telescope”

- Angular resolution ~ 1 degree

- Pointing Accuracy ~ 1 degree

- Charged Messengers => deviation in mag. fields

Exposure of the experiment in Galactic coordinates

The (Aug. 2007) astronomy analyses

~9000 km2 sr yr, trigger efficiency ~100%

Search for point sources:the motivation

Small magnetic deflection Only nearby sources if GZK feature ok Nearby Universe anisotropic

1 EeV =1018 eV

Regular Gal. B field

Search for point sources:the motivation

Small magnetic deflection Only nearby sources if GZK feature ok Nearby Universe anisotropic

Indication of GZK from spectrum Bounds on photons/neutrinos Acceleration favoured vs. top-down

1 EeV =1018 eV

Regular Gal. B field

Search for point sources:the method

Need to search correlations of a selected sample of events with astrophysical objects.... how and where?

Large parameter space: -- events -> Energy, angular aperture

Sources -> what sources: type, distance (z)........


Need to search correlations of a selected sample of events with astrophysical objects.... how and where?

Large parameter space: -- events -> Energy, angular aperture

Sources -> what sources: type, distance (z)........

Method: perform a scan in the parameters space, after having chosen sources of a given type from a catalogue

Chosen Veron-Cetty, Veron Catalogue of AGNs


Some definitions: p -- exposure-weighted fraction of the sky accessible to observation, covered by windows of radius ψ centred on the selected sources. P -- probability that k or more out of a total of N events from isotropic flux are correlated by chance with the selected objects at the chosen angular scale

this probability needs 'penalization' i.e. Pfin

= P/Nt (from MC)

z<0.018

Search for point sources:the strategy

Performed an exploratory scan. Eth > 4 1019 eV

z < 0.024 Of 15 events with Eth > 5.7 1019 eV,

12 correlated within with AGNs with z<0.019, while 3.2 expected with these parameters

16

3.1o


Performed an exploratory scan. Eth > 4 1019 eV

z < 0.024 Of 15 events with Eth > 5.7 1019 eV,

12 correlated within with AGNs with z<0.018, while 3.2 expected with these parameters

Further search performed with these a priori fixed parameters, ending when the probability to incorrectly reject hisotropy hypotesis < 1%

Search started May 2006, ended May 2007 when 6/8 events found correlating.

In sample May 2006 – Aug 2007 8/13 correlating P= 1.7 10-3

16

3.1o


Rescan whole dataset with improved reconstr. algorithm to fix parameters.

20 out of 27 events correlated

(a posteriori) Pfin(iso)~10-5

Search for point sources:the PAO Sky Map

Equatorial coordinates

South pole

SuperGalactic plane

Galactic plane


PAO events


AGNs from VC-V catalogue (z<0.018)

PAO events


CenAVirgo

AGNs from VC-V catalogue

PAO events


CenAVirgo


If region of Galactic plane excluded, 19 out of 21 events do correlate

PAO events


CenAVirgo


Leiden – Argentine – Bonn Hydrogen Survey

PAO events


Both for real events and simulated sets of same size, either isotropic or source

CenA



AGNs: sources or tracers??


AGNs: sources or tracers??No significant correlation (yet) with Abell,REFLEX, NORAS catalogues of clusters of galaxies, nor starburst radio galaxies


CenA


The GZK “horizon”


The GZK “horizon”

Indication of the need of energy shift?Too early, exclude other selection effects (foreground, bias of method..)


Magnetic fields

Extragalactic (irregular)


Magnetic fields

Extragalactic (irregular)

B rms L c10−9 G Mpc

Possibly Some open issues:-- Statistic: 27 events E> 5.7 1019 eV. One more year of data will double N.

Birth of (nuclear) Cosmic Ray Astronomy?

Possibly Some open issues:-- Statistic: 27 events E> 5.7 1019 eV. One more year of data will double N.-- Energy: at 5.7 1019 eV GZK Horizon ~ 200 Mp > 75

upward shift of energy calibration consistent with sistematic error can reconcile


Possibly Some open issues:-- Statistic: 27 events E> 5.7 1019 eV. One more year of data will double N.-- Energy: at 5.7 1019 eV GZK Horizon ~ 200 Mp > 75 but...

upward shift of energy calibration consistent with sistematic error can reconcile-- Type of particles: some hint of heavy nuclei, larger deviation in GMF


HiRes does not confirm

We are probably at a turning date for Cosmic Ray Astrophysics Sources of Cosmic Rays may have been detected, although their real identity

still unclear The Greisen-Zatsepin-Kuzmin feature has been probably detected

Conclusions?

We are probably at a turning date for Cosmic Ray Astrophysics Sources of Cosmic Rays may have been detected, although their real identity

still unclear The Greisen-Zatsepin-Kuzmin feature has been probably detected

A very interesting future is approaching!!

Conclusions?


Magnetic fields

Difficult – impossible if nuclei


Magnetic fields


Magnetic fields

Problem not serious (yet!) also: non correlating events chance correlating events

Preliminary!!

HiRes HiRes energy x 0.83

CenA


Preliminary!!

No distinctive feature of correlated AGNs identified. AGNs: sources or tracers?

La nascita della astronomia dei raggi cosmici? Indicazioni dall' Osservatorio P. Auger

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