[PPT] - Transition from Galactic to Extragalactic Cosmic Rays Roberto PowerPoint Presentation

SLIDE 1

Roberto Aloisio

Transition from Galactic to Extragalactic Cosmic Rays

Symposium 20th Anniversary of the Foundation of the Pierre Auger Observatory

14-16 November 2019, Malargue, Mendoza Province, Argentina.

INFN – Laboratori Nazionali del Gran Sasso Gran Sasso Science Institute

SLIDE 2

CR Observations and the transition GCR-EGCR

ü The all particle

spectrum is a broken power law with few structures: knee, second knee, ankle, strong suppression at UHE.

ALL PARTICLE SPECTRUM

KNEE

T R A N S I T I O N

ANKLE II KNEE In Cosmic Rays physics we can study sources, production mechanisms and the physics

f

propagation only through three basic observables

üSpectrum üAnisotropy üMass composition

SLIDE 3

E [eV]

17

10

18

10

19

10

20

10

]

2

eV

1

sr

1

yr

2

[km

3

E × J(E)

37

10

38

10

(E/eV)

10

log

17 18 19 20

< 60 degrees θ SD 1500m SD 750m Cherenkov > 60 degrees θ SD 1500m hybrid

Auger Collaboration (2019)

Ultra High Energy Cosmic Rays – Spectrum

ü Expected changes in the mass

composition across the transition region: from heavy to light (see later).

ü Anisotropy observations can

provide stringent limits on the transition region.

Transition GCR-EGCR

ü Second knee: ~2x1017 eV ü Ankle: ~3x1018 eV

Spectral features

SLIDE 4

ü Large scale anisotropy: dipole E>8 EeV (5.2!) Extragalactic origin

Auger Collaboration (2019)

Ultra High Energy Cosmic Rays – Anisotropy

0.36 0.40 0.44 Flux[km-2 sr-1 yr-1]

90

90 360

ü Intermediate anisotropy: E>38 EeV (3.8!) Hints of sources (Starburst, AGN)

SLIDE 5

E [eV]

17

10

18

10

19

10

20

10

]

2

eV

1

sr

1

yr

2

[km

3

E × J(E)

37

10

38

10

(E/eV)

10

log

17 18 19 20

< 60 degrees θ SD 1500m SD 750m Cherenkov > 60 degrees θ SD 1500m hybrid

Dipole: Extragalactic Hotspot: Sources

SLIDE 6

E. G. Berezhko, H. J. Volk (2008)

Galactic CR: knees and acceleration

ü The knee as a signature of a rigidity

dependent acceleration

ü The all particle spectrum is the result of

the sum of the spectra of different species, with a cut-off energy rigidity dependent

EZ = ZEp

J.R. Horandel et al. (2003)

üMaximum energy of accelerated protons

(need for “Pevatron” sources)

Ep

0 & 1PeV

dΦZ dE (E) = Φ0

XE Z

 1 + ✓ E EZ ◆✏c− ∆

✏c

SLIDE 7

U1 U2

X-rays observations

Typical size of the observed filaments ~ 10-2 parsec

Diffusive Shock Acceleration

100 20 40 60 80 100

40.5
40
39.5
39

17h10m 17h15m

PSF

RXJ-1713, X and gamma Tycho, X

Comparison with the observed thickness leads to a B-field estimate

B ' O(100µG)

ü Diffusion of charged particles back and forth

through the shock leads to

ü Particles are accelerated to a power law

spectrum

ü The slope of the spectrum depends only on

the shock compression factor, in the case of strong shock (M>>1) Q~E-2 .

ü The maximum acceleration energy depends

nly on diffusion in the shock region. The

ISM magnetic turbulence (as it follows from B/C observation) is too low (providing only CR at GeV energy). It is needed additional turbulence to reach Emax ~105-106 GeV.

Q(E) ∝ E−γ

∆E ' E(4/3)(U1 U2)/c

SLIDE 8

Morlino & Caprioli 2011

Steep spectrum hard to explain with leptonic emission

The case of Tycho

ü SNIa exploded in roughly homogeneous ISM

(regular spherical shape)

ü From X-ray observations B~300 µG ü Maximum energy protons Emax~500 TeV ü Leptonic emission. ICS of relativistic electrons

n photon background has a flatter spectrum

respect to CR: E-(γ+1)/2

ü Hadronic emission. pp→π0→γγ conserves the

same spectrum of CR: E-γ

ü Important experimental confirmation of the

credibility level of theories based on DSA. Space resolved gamma ray observations would test different theoretical hypothesis.

Xray profile 1 keV

0.94 0.95 0.96 0.97 0.98 0.99 1.00 1 2 3 4 5 6 7 8 RRsh Brightness ergscm2Hzsr

4.

Morlino & Caprioli 2011

SLIDE 9

ESCAPE FLUX FROM BOUNDARY ESCAPE FROM SNR AFTER EXPANSION

Escape of CR from accelerator – maximum energy

Caprioli et al. 2009

Escape is the physical phenomenon that transforms accelerated particles into CR. CR injected

ü particles escaped during the

free expansion and Sedov- Taylor phases (emission peaked on pmax)

ü particles released in the ISM

after expansion Streaming instability Super-Alfvenic streaming

f

CR leads to the excitation of magnetic turbulence δB at the resonant wavenumber k=1/rL. Locally at the shock front this turbulence can reach δB/B ~ 50, while in the ISM δB/B<<1. Maximum energy

ü particles escape ü NOTE: Hillas criterion

is an upper limit,

verestimates the actual maximum energy by a factor of c/Vsh

D(Emax) Vsh ' χRsh χ < 1

rL(Emax) = Rsh

SLIDE 10

Blasi 2019

Galactic CR acceleration

ü In the framework of DSA

in SNRs the maximum attainable energy seems somewhat lower than needed. ü Type Ia SN ü Type II SN core collapse in its own wind

Ep

max = 0.05

✓ξCR 0.1 ◆ ✓Mej M ◆2/3 ✓ ESN 1051erg ◆ ⇣nISM cm3 ⌘ PeV

Ep

max = 0.3

✓ξCR 0.1 ◆ ✓Mej M ◆1 ˙ M 105Myr1 !1/2 ✓ ESN 1051erg ◆ ✓ Vw 10kms1 ◆ PeV

SLIDE 11

(E/TeV)

10

Log 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 )

1

sr

1

s

2

m

1.6

(GeV Ω dAdtd

E

d dN ×

2.6

E

2

10

3

10

4

10

ARGO-YBJ G4 ARGO-YBJ G1 ARGO-YBJ Bayes-G4 ARGO-YBJ Bayes-G1 ARGO-YBJ WFCTA (p + He) ARGO-YBJ strip (p + He) Tibet III (QGSJET-II) 2008 Tibet III (SIBYLL) 2008 KASCADE (QGSJET-II) 2005 KASCADE (SIBYLL) 2005 Tunka-25 2013 Tunka-133 2012 DICE 2000 Icetop 2013 KASCADE-Grande 2012 EAS-Top 1999 BLANCA 2001 CASA-MIA 1999 RUNJOB JACEE KASCADE p KASCADE (He + C + Si) KASCADE Fe YAC-I TibetIII (p + He) SIB 2013 CREAM (p + He) 2011 Horandel (p + He) 2003 1 PeV × knee at Z Horandel (p+He) 2003 Horandel (All particle) 2003 Gaisser et al. 2013 (p + He) Gaisser et al. 2013 (p+He+Fe+CNO) Direct measurements comb. (p + He) Direct measurements (All particle)

Preliminary

Galactic Cosmic Rays – The knee structure

All particle and light components (Argo-YBJ) P+HE SPECTRUM (YAC1-Tibet)

I. De Mitri, A. D’Amone, L. Perrone, A. Surdo (2016)
J. Huang (2013)

ü Knee in the all particle spectrum ~ 2 PeV ü Knee in the light component ~ 0.1 PeV

YAC1-Tibet and Argo-YBJ

SLIDE 12

Energy (eV/particle)

13

10

14

10

15

10

16

10

17

10

18

10

19

10

20

10

21

10

)

1.5

eV

1

sr

1

sec

2

J(E) (m

2.5

dI/dE x E

13

10

14

10

15

10

16

10

17

10

18

10

19

10

direct data

Akeno (J.Phys.G18(1992)423) AGASA (ICRC 2003) HiResI (PRL100(2008)101101) HiResII (PRL100(2008)101101) AUGER (ICRC 2009)

EAS-TOP (Astrop.Phys.10(1999)1) KASCADE (Astrop.Phys.24(2005)1) KASCADE H KASCADE He KASCADE heavy TIBET-III (ApJ678(2008)1165) GAMMA (J.Phys.G35(2008)115201) TUNKA (ICRC-Beijing(2011)) IceTop (2012-arXiv:1202.3039v1) Yakutsk (NewJ.Phys11(2008)065008) KASCADE-Grande (QGSJET II) Nch-N KASCADE-Grande heavy KASCADE-Grande light+medium

Kascade and Kascade-Grande

A. Haungs et al. (2013)

ü The position of the p+He

knee is not clearly determined, discrepancies among experiments (high vs low altitudes?)

ü Uncertainties in the

hadronic interaction models

ü Uncertainty in the maximum

acceleration energy of galactic CR.

ü Knee in the all particle

spectrum ~ 2 PeV

ü Knee in the heavy

component ~ 80 PeV

ü ”Recovery” in the light

component ~ 100 PeV

(E/eV)

10

log 16.4 16.6 16.8 17 17.2 17.4 17.6 17.8 18 18.2 18.4 )

1.7

eV

1

s

1

sr

2

(m

2.7

dI/dE x E

18

10

19

10

all-particle -- PRL 107 all-particle heavy (sep. between He-CNO) light (sep. between CNO-Si) -- PRL 107 light (sep. between CNO-Si) light (sep. between He-CNO) light (sep. on He)

(E/eV)

10

log 16.6 16.8 17 17.2 17.4 17.6 17.8 18 18.2 )

1.7

eV

1

s

1

sr

2

(m

2.7

dI/dE x E

19

10

light (sep. between He-CNO) band of systematic uncertainty 0.08 ± /eV) = 17.08

break, light

(E

10

0.08, log ± = -2.79

2

γ 0.05, ± = -3.25

1

γ 2506 1487 882 539 322 195 144 92 55 43 40 18 8

W.D. Apel et al. (2013)

Kascade and Kascade -Grande

SLIDE 13

Ultra High Energy Cosmic Rays – Composition

Auger Collaboration (2019)

At the lowest energies log(E/eV)=17.5 an increasing light component till log(E/eV)=18.5, with increasing energy the composition turns heavier. Uncertainties due to the hadronic interaction model assumed.

Mixed Composition

SLIDE 14

RA, Berezinsky, Grigorieva (2009-2013)

Critical Lorentz factor

The critical Lorentz factor fixes the scale at which photo-disintegration becomes relevant, for heavy nuclei it is almost independent of the nuclei specie It is impossible to observe at the Earth a pure heavy nuclei spectrum, even if sources inject only heavy nuclei of a fixed specie at the Earth we will

bserve all secondaries (protons too)

produced by photo-disintegration.

Composition

Caveats on UHE nuclei

SLIDE 15

1037 1038 1039 1040 1018 1019 1020 E3 J(E) (arb. norm.) E (eV) He

γ=1.0 γ=2.0 γ=2.5

1037 1038 1039 1040 1018 1019 1020 E3 J(E) (arb. norm.) E (eV) CNO

γ=1.0 γ=2.0 γ=2.5

1037 1038 1039 1040 1018 1019 1020 E3 J(E) (arb. norm.) E (eV) MgSi

γ=1.0 γ=2.0 γ=2.5

1037 1038 1039 1040 1018 1019 1020 1021 E3 J(E) (arb. norm.) E (eV) Fe

γ=1.0 γ=2.0 γ=2.5

L0 = nUHELUHE = AmN Z Γmax

1

dΓΓQA(Γ)

QA(Γ) = Q0e−Γ/Γmax ✓ Γ Γ0 ◆−γg

The combined effect of nuclei energy losses, mainly photo-disintegration, and injection implies that a steep injection increases the low energy weight of the mass composition

Injection of nuclei: flat vs steep

The effect of an Intergalactic Magnetic Field (IMF) can mitigate the conclusion on flat spectra allowing for steeper spectra γ≈2.

Note

SLIDE 16

1021 1022 1023 1024 1025 1018 1019 1020 1021 E3 J(E) (eV2 m-2 s-1 sr-1) E (eV)

γg=1.0, Emax=5Zx1018 eV p He CNO MgAlSi Fe

10 20 30 40 50 60 70 1018 1019 1020 σ(Xmax) (g/cm2) E (eV)

What we can learn from Auger data

RA, Blasi, Berezinsky (2014) 650 700 750 800 850 1018 1019 1020 <Xmax> (g/cm2) E (eV) EPOS Sybill QGSJet1 QGSJet2

Auger chemical composition can be reproduced only assuming a very flat injection of primary nuclei

γg = 1.0 ÷ 1.5

with a certain level of degeneracy in terms

f the nuclei species injected

L0 = nUHELUHE ' 1044 erg Mpc3y

SLIDE 17

650 700 750 800 850 1018 1019 1020 <Xmax> (g/cm2) E (eV) EPOS Sybill QGSJet1 QGSJet2 1021 1022 1023 1024 1025 1018 1019 1020 1021 E3 J(E) (eV2 m-2 s-1 sr-1) E (eV)

γg=1.0, Emax=5Zx1018 eV gal p He CNO MgAlSi Fe

10 20 30 40 50 60 70 1018 1019 1020 σ(Xmax) (g/cm2) E (eV)

An additional galactic component can fill the gap in the spectrum. Composition issue. Mixture of 80% p and 20% He to reproduce Auger

bservations. Difficult to reconcile

with DSA acceleration and anisotropy

bservations.

RA, Blasi, Berezinsky (2014)

Extra Galactic Nuclei and Galactic light elements

SLIDE 18

The Kascade-Grande observations seem to confirm the presence of an extragalactic light component with a steep injection spectrum.

1018 1019 1020 1016 1017 1018 E2.7 J(E) (eV1.7 m-2 s-1 sr-1) E (eV)

KG light 5 PeV 6 PeV 7 PeV p+He, extra gal

ü light component steep injection (γg>2.5) ü heavy component flat injection (γg<1.5)

L0 = nUHELUHE ' 1044 erg Mpc3y L0 = nUHELUHE ' 1047 erg Mpc3y

1021 1022 1023 1024 1025 1018 1019 1020 1021 E3 J(E) (eV2 m-2 s-1 sr-1) E (eV)

γg(p,He,A>4)=1.0, γg(p,He)=2.7 Emax(p,He,A>4)=5Zx1018 eV, Emax(p,He)=3Zx1019 eV

Fe, gal p He CNO MgAlSi Fe

650 700 750 800 850 1018 1019 1020 <Xmax> (g/cm2) E (eV) EPOS Sibyll QGSJet1 QGSJet2 10 20 30 40 50 60 70 1018 1019 1020 σ(Xmax) (g/cm2) E (eV)

RA, Blasi, Berezinsky (2014)

Different Classes of Extra Galactic Sources

SLIDE 19

Transition at the ankle

ü Galactic light component between

0.1 EeV<E< 1 EeV.

ü Difficult to reconcile with anisotropy

and mass composition observations.

ü New kind of galactic very high

energy sources. Not compatible with the standard model of DSA.

Transition at the II knee

ü Different

injection light/heavy (steep/flat) (Two classes

f

extragalactic sources and/or specific dynamics at the source).

ü Compatible with Kascade-Grande

bservations.

ü Not too demanding respect to the

standard model of DSA.

1022 1023 1024 1025 1015 1016 1017 1018 1019 1020 1021 E3 J(E) (eV2 m-2 s-1 sr-1) E (eV)

p He CNO MgAlSi Fe

1022 1023 1024 1025 1015 1016 1017 1018 1019 1020 1021 E3 J(E) (eV2 m-2 s-1 sr-1) E (eV)

p He CNO MgAlSi Fe