CTA Science Cases for Ultra-high-energy Cosmic Rays
Hajime Takami
KEK, JSPS Fellow

1Outline• Current understandings on ultra-high-energy cosmic rays
• Multi-messenger approaches to UHECRs• Gamma-ray emission accompanying UHECR acceleration• Hadronic gamma-ray emission from blazars / AGN• Cosmic-ray-induced cascades• Neutron-star-binary mergers -- connection to GW

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 20132

Cosmic rays

Ultra-high-energy

Highest energy

LHC(CMS)

LHC(Lab.)Bhattacharjee & Sigl (2000),
originally from S. Swordy

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 20133

00 m a.s.l.

tor (SD)UHECR Spectra

ator SDsng

17.5
pectrum E > 10eV1277 Letessier-Selvon
0928 Verzi, 0769 Schulz
0693 Ravignani0128 Sagawa, 0221 Bergman

oector(FD)• Auger energy-scale updated by (10-16)%

es

n
es

THE
m
ATORY
(BR)
tion
3

hts ICRC 2013 Rio de Janeiro

IC

3
1
0
2
C
R
2013 prelim.

• Auger energy uncertainty improved to 14%• Marginally consistent between Auger and TA• Steepening at ~1020 eV• Dip at ~ 1018.5 eV

5 years

Tsunesada, ICRC
201315

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
4

UHECR Composition

Updated Measurement of hXmax i and (Xmax )Still inconsistent between Auger and TA〈Xmax〉 [g/cm2]

Auger

840

EPOS-LHCQGSJetII-04
Sibyll2.1

820
800

pro

σ(Xmax) [g/cm2]

comparison to air shower simulations
ton

780
760

90

Auger 2013 preliminary

FD stereo Xmax

80
70

proton

60

TA

50

740

iro

720

40

n

30

700

20

680

Measurement of hXmax i and (Xmax )

iron
10

660

10

POS-LHC
GSJetII-04
byll2.1

σ(Xmax) [g/cm2]

on to air shower simulations
ton
o
r
p

iro

18

10

19

10

20

E [eV]

90

0

10

18

10

19

10

20

E [eV]

Auger 2013 preliminary[8 of 15]8070

proton

60
50
40

n

Sagawa, ICRC 2013

30
20

iron
10

10

19

10

20

0

10

Ahn, ICRC 2013
E [eV]

18

10

19

10

20

E [eV]

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
[8 of 15]5

Anisotropy
Small-scale

E > 57 EeV
AGN correlation
Far from isotropic sources~3V

Roth, TeVPA 2013

Sagawa, ICRC 2013

Large-scale: first harmonics

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 20136

Remaining Problems on UHECRs• What is the maximum energy of UHECRs?
• What is the composition of UHECRs?

What is the sources of UHECRs?

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 20137

Possible Highest-energy CR Sources
Only extreme phenomena in the Universe can produce UHECRs.
Active Galactic Nuclei

Gamma-ray bursts

e.g., Biermann & Stritmatter ‘87, Takahara ‘90,
Rachen & Biermann ‘93, Farrar & Gruzinov ‘09,
Dermer et al. ’09, Pe’er et al. ‘09,
HT & Horiuchi ’11, Murase et al. ‘11e.g., Waxman ‘95, Vietri ’95,
Murase et al. ’08, Wang et al. ‘08

Neutron stars / Magnetars

Cluster of galaxies
JEM-EUSO Purple booke.g., Blasi et al. ’00, Arons ‘03,
Kotera ‘11, Fang et al. ‘12e.g., Norman et al. ‘95, Kang et al.
‘96, Inoue et al. ‘07

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
8

What we have learned from UHECR measurements• Some (extreme) composition models have not been favored (spectrum, composition)
Allard et al. 2008, Hooper et al. 2009, ...

• Apparent local source number density• (>)~ 10-4 Mpc-3 for small deflection (~protons)
HT& Sato 2009, Cuoco et al. 2009, Abreu et al. 2013•>~ 10-7 Mpc-3 for heavy nuclei (highly dependent on B models)HT, Inoue, Yamamoto 2012

Objects

ns [Mpc-3]

Major galaxies~ 10-2Bright galaxies

1.3 x 10-2

Seyfert galaxies

1.25 x 10-2

Dead quasars

5 x 10-4

Fanaroﬀ-Riley I

8 x 10-5

Cluster of galaxies

1 x 10-6

Bright quasars

1.4 x 10-6

Colliding galaxies

7 x 10-7

BL Lac objects

3 x 10-7

Fanaroﬀ-Riley II

3 x 10-8

See Yoshida & Ishihara (2012) for a neutrino constraint

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 20139

Source-identification ability of UHECRs
Averaged occupation of UHECR sources in the sky > Deflection angles
600

21
Emax = 10eV
20.5
Emax = 10
eV

Dmax(E) [Mpc]500

Dmax(E)• 99% cosmic rays included• Uniform distribution
Occupation

400
300

4⇡ 3
Dmax (E)ns ⌦ = 4⇡
3

200

Deflection (extragalactic)

100
0
19.6

Angular distance / Deflection [deg]

103

102

19.8

20
log10(E [eV])

20.2✓(E) = 2.5

20.4

HT & Murase 2012

E1020 eV◆ 1✓

Dmax (E)
100 Mpc◆1/2 ✓

B
1 nG

◆✓

1 Mpc

◆1/2

B 1/2 ⇠ 0.3 nG Mpc1/2 from Ryu et al. (2008) simulations

Occupation for ns = 10-4 Mpc-3
Extragalactic (B h1/2 = 0.3 nG Mpc1/2)
Galactic (BS-S)
68%
95%

HT & Murase 2012

1. Huge statistics at E > 1020 eV
JEM-EUSO, TA2, Auger-next, ...

101

2. Other messengers
Gamma rays, neutrinos, ...

100

10-1 1910✓1020
Energy [eV]1021

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201310

Transient Sources
A stronger anisotropy appears at higher energies .
•

•

10

ns(E) ~ source number density estimated on the assumption of steady sourcesρs : UHECR burst rate ( source property instead of ns in steady source cases)
Higher energy CRs-2

Shorter apparent duration

ns(E) [Mpc-3]

anisotropy

10-3s = 102 Gpc-3 yr-1

10-4

Smaller probability to observe a UHECR burst
s = 1 Gpc-3 yr-1

10-5
10-6
10-7

Bursting case

19.6

19.8

20
log10(E [eV])<1 source
within Dmax(E)
20.2

20.4

Smaller number of “point source”-like features+ GZK mechanism
Stronger anisotropy ( smaller ns(E) )HT & Murase 2012

The dependence of ns(E) is evidence of transient generation of UHECRs.
ns(E) should be estimated in at least two energy ranges.
Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
11

PeV
neutrinos
Proposed source candidates• extragalactic sources:• relation to the sources of UHE CRs[Kistler, Stanev & Yuksel 1301.1703]• GZK from low Emax blazars[Kalashev, Kusenko & Essey 1303.0300]• cores of active galactic nuclei (AGN)[Stecker et al.’91;Stecker 1305.7404]• low-power -ray bursts (GRB)[Murase & Ioka 1306.2274]• starburst galaxies[Loeb&Waxman’06; He et al. 1303.1253; Murase, MA & Lacki 1306.3417]• galaxy clusters/groups[Berezinksy, Blasi & Ptuskin’97; Murase, MA & Lacki 1306.3417]• Galactic sources:• heavy dark matter decay[Feldstein et al. 1303.7320; Esmaili & Serpico 1308.1105]• peculiar hypernovae[Fox, Kashiyama & Meszaros 1305.6606; MA & Murase (in prep.)]• diffuse Galactic -ray emission[e.g. Ingelman & Thunman’96; MA & Murase (in prep.)]•

Ep ~ 20 Eν ~ 1016 - 1017 eV-ray association:• unidentified Galactic TeV -ray sources• sub-TeV diffuse Galactic -ray emission

Markus Ahlers (UW-Madison)

Skymap:Noexcess”
Significant Clustering“IceCube[Fox, Kashiyama & Meszaros 1306.6606][Neronov, Semikoz & Tchernin 1307.2158]

Multi-Messenger Tests of the IceCube Excess

August 29, 20135

Markus Ahlers, TeVPA 2013

[C.Kopper, N.Kurahashi & N.Whitehorn, IPA’13]

Markus Ahlers (UW-Madison)

Multi-Messenger Tests of the IceCube Excess

August 29, 2013

2

See: talk by Naoko Kurahashi Neilson
IPA 2013 - 3

Whitehorn, UW Madison
Hajime Takami | CTA workshop 2013 @ ICRR, the University ofN.Tokyo,
Japan, Sep. 3, 201312• Gamma-ray emission accompanying UHECR acceleration• Hadronic gamma-ray emission from blazars / AGN• Cosmic-ray-induced cascades (AGN)• (Neutron-star-binary mergers if time is allowed)

13

Active Galactic Nuclei• Luminous nucleus comparable with the whole galaxy• Powered by accretion onto supermassive black holes• Some AGN (radio galaxies) have jets.

Unification Hypothesis
The diversity of AGN originates from theviewing angle of observers.
Urry & Padovani 1995

Blazars - AGN with jets directed to observers

Relativistic jets--> Relativistic beaming is essentially important.

http://w3.iaa.es/~jlgomez14

Typical SED and Blazar Sequence
Spectral Energy Distribution
Two humps

FSRQ• Lower freq. - Electron synchrotron radiation• Higher freq. - Inverse Compton / Hadronic
LBL

HBL

Blazar sequence
Empirical relation:
The lower peak frequency is, the higher
luminosity is.

Fossati+ 1998

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201315

Emission Models of Blazars

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201316

SED Modeling of Mrk 421
Leptonic model

Hadronic model

π±
π0

p-syn
μ-syn

Abdo+ 2011•

Spectral fit → Physical parameters•

Both models can reproduce the SED.

•

Hadronic models usually require UHECRs.
Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201317

(Lepto-)Hadronic Model for BL Lac
The Astrophysical Journal, 768:54 (14pp), 2013 May 1

Böttcher et al.

Leptonic modeltvar ~ 1.5 hr

BL Lacertae

14

10

13

13

12

10

11

10

10

Le [erg/s]

4.4 x 1043

12

10

-

Lp [erg/s]

8.7 x 1042

9.8 x 1048

B [G]

2.5

10

δ

15

15

γmin

1.1 x 103

7 x 102γmax

1 x 105

1.5 x 104

11

10

10

9
10

10

12

10

14

10

16

10

18

10
ν [Hz]

20

22

10

10

24

10

9

10

26

10

10

10

12

10

14

10

The Astrophysical Journal, 768:54 (14pp), 2013 May 1

Hadronic modelS5 0716+714
BL Lacertae

14

1014
10

1013
10

13

10
13
10

12
1012

12

10 qe 10
ν [Hz]
Emax
16

18

20

10

10 3.210
22

24

26

10

3.5

B
-öttcher et al.2 x 1018

OJ 287
AO q
0235+164
p

14

10
14
10

-

2.4

13

[Jy[JyHz]Hz]
νFννF

Hadronic model

10
12
10

10

• Lp = π R2 β c np mp c2• μ-synchrotron, π-synchrotron are neglected.
• Simpler semi-analytical method --- parameter fits
• Only available cases are considered• Cascade in the emission region

ν[Jy[Jy
Hz]
νFνF
Hz]
ν ν

Hadronic

10

10

11

1011
10

11

10
11
10

10

10

1010
10

10
10
10

9

109
10

Leptonic

10

νFν [Jy Hz]

νFν [Jy Hz]

1010

AO 0235+164

14

10

9

10
1010

10

12
1012

10

14
1014

10

16
1016

10

18
1018

ν [Hz]
10
ν [Hz]

20
1020

10

22
1022

10

24
1024

10

26
1026

10

10
9
10

10

10
10
10

12

10
12
10

14

10
14
10

16

10
16
10

18

20

10
10
18
20
ν10
[Hz]
10
ν [Hz]

22

10
22
10

24

10
24
10

26

10
26
10

Figure 5. Leptonic model fits to the four LBLs in our sample.Böttcher
See Table 2 foret parameters.
al. 2013 Dotted: synchrotron; dashed: accretion disk; dot-dashed: SSC; dot-dash-dashed:
EC (disk); dot-dot-dashed: EC (BLR).S5 0716+714
OJ 28714
14(A color
is available
in the online
journal.)10version of this figureHajime
Takami| CTA
workshop 2013 @ 10ICRR, the University of Tokyo, Japan, Sep. 3, 2013
14
10 13

10

W Comae

14
1013

10

3C66A
18

UHECR Acceleration in SSC blobs
Hadronic scenarios --> hint of unknown UHECR sources

Dermer, Murase, HT, Migliori 2012

The highest energy CRs are diﬃcult to be accelerated in the SSC blobsof BL Lac objects / FR I galaxies.
Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201319

Extreme HBL
Highest-frequency-end of the blazar sequence
1ES 0229+200 (z = 0.14)
Γ = 2.50 ± 0.19stat ± 0.10sys(500 GeV - 15 TeV)z ~ 0.2• Very hard TeV spectra beyond ~10 TeV• No significant variability• Faint in the Fermi range

Aharonian et al. 2007

1ES 0347-121 (z = 0.188)
Γ = 3.10 ± 0.23stat ± 0.10sys(250 GeV - 3 TeV)

Aharonian et al. 2007

1ES 1101-232 (z = 0.186)
Γ = 2.94 ± 0.20(> 225 GeV)

Aharonian et al. 2007

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201320

Mean free path and optical depth of gamma rays
L10

Mean free path

COPPI & AHARONIAN

Vol. 487ÍNGUEZ] ET AL.
Attenuation energy [DOM
τ(E,z)=1

10

Cosmic γ-ray horizon, E0 [TeV]

z=0This work
Domı́nguez+ 11
10

n42
Mk

1
n50
Mk

1

PK

00
S2

5-4

89

1
PK

15
S2

1E

0.1
0.01

5-3

S

04

6+
080

524

0.1
Redshift4+3 0
218 32
1S
2
1E 1011
S
1E

3C

66A
3
155
PG

+1 1

3

1

Fig. 2.— Estimation of the CGRH from every blazar in our sample plotted with blue Dominguez
circles. The statisticaluncertainties are show
et al. 2013
darker blue lines and the statistical plus 20% of systematic uncertainties are shown with lighter blue lines. The CGRH calculate
the EBL model described in Domı́nguez et al. (2011a) is plotted with a red-thick line. The shaded regions show the uncertainties fr
FIG. 1.—Local pair-production mean free path, l, for
VHE
photonsof
Coppi
Aharonian
1997
EBL&modeling,
whichwere derived from observed data.

energy, E, at redshift z 5 0 (no cosmological effects included). Below 1014 eV,
19 blazar spectra since it allows us a wider range ofdom, see Table 1. The uncertainties of the two
VHE photons interact primarily with IRyO photons; aboveon10theeV, they14
19
spectralindices(i.e.,
thisresultsinaratherconservative
redshift blazars (Mkn 501 and Mkn 421) are syste
interact with radio photons; between 10 and 10 eV, they interact with MBR
For this same reason, wecally higher because the optical depth for these cas
photons. Curves a, b, and c, respectively, show l for the IRyOhypothesis
backgroundsforof our analysis).
FIG. 2.—The cutoff energy, Ecut, as a function of source redshift, z, forprefertouse
asconservative
upper
limitstheresultsbycomes unity at energies
larger than the energies obs
curves (i), (iv), and (vi) inVery-high-energy
Fig. 2. Curves 1, 2, and 3 show,respectively,
l for thephotons
(>100
GeV)
are
absorbedvia
paircreation,different
IRyO DEBRAs
in an V
5 1 universedepending
with H0 5 75 kmon
s21 Mpc21. Ecut
&SimonRaue (2007) rather than the newer results byby the Cherenkov telescopes. Therefore, in these
extragalactic radio background estimate of Sironi et al. (1990) Mazin(see also
is given by tgg[(1 1 z) Ecut, z] 5 1, where tgg is the optical depth for photon
sourceredshift,
extragalactic
light. τ = 1 is given by an extrapolation of the polyno
Meyer etal.by(2012)
thatare basedbackgroundon a more constrain1977) with a low-frequency cutoff at 5, 2, and 1 MHz.
The triangles
givetheabsorption via pair production. Curves (i) and (vi) show Ecut for roughly theing spectral
condition.minimum
The EBLevolutionisexpectedto (Dwek
ratherthan1994)
an interpolation
lower limit on l obtained assuming the total observed radio background(e.g.,(Tyson 1995) and maximum& Slavinallowed IRyObetween observed en
Ressell & Turner 1991) is extragalactic. The heavy dotted affectline shows
the depth
the optical
calculated
Tocm23 for(see(i)Fig.
2 higher redshifts.
levelstoday: eatn(e, 0) 5 1 3 1023 eVand1)e 2leadingn (e, 0) to
5 greater
1 3 1022uncertainty. For the cenergy-loss mean free path forenergetic
protons.
23
3
account 2013
for this@effectwecm
evolvethe evolves
EBL
1ES
fast
variability timescale, aHajime Takami | CTA workshop
ICRR,
the
University
Tokyo,
Japan,
Sep.
eV
for conservatively(vi). The of
DEBRA
as n(
e, z)2344+514
53,(120131 z) withn[ey(1
1 fluxz), 0],

upper limits at all wavelengths
as (1z)5 (in theco- Curveof (v)
E0 isinthe
agreement
withexcept
the estimation by the D11
and n(e, 0) has
no +opticalyUV
cutoff.
same as (vi),moving frame) when thecalculating
the opticaldepthsis derived.
However,
for this case the uncerta
IRyO DEBRA
is formed
in froma burst at modelz 5 5 withno photons
emittedthese
EBL limits from
Mazin
&
Raue
(2007).
Wenote
arelargerthanE
andtherefore
no useful constrai
rived, despite the uncertainties in the DEBRA. We
summarize
21
0 cut for more
above the Lyman limit (13.6 eV). Curves (ii)–(iv) show E

Gamma-ray-induced Cascade

Pair creation! e+ eCMB / EBLγγ

CMB / EBL
Created pairs are aﬀected by intergalactic magnetic magnetic fields if they are strong enough.

• Pair-halo : image spread (e.g., Aharonian Coppi, Völk 1994, Elyiv et al. 2009)• Pair-echo : delayed secondary gamma rays (e.g., Plaga 1995, Murase et al. 2008, Ichiki et al. 2008)• IGMF study : gamma rays from deflected pairs do not reach the earth if IGMF is suﬃciently strong(e.g., Neronov et al. 2009, Dermer et al. 2011, Dolag et al. 2011), but possible plasma instability
causes the deflection (under debate; e.g., Schlickeiser et al. 2013 for a recent discussion)

22Gamma-ray-induced Cascade-7

z=0.05
z=0.1
z=0.3
z=0.5
z=0.7

log(E2 FE [GeV cm-2 s-1])-8-9• The cascaded spectra are strongly attenuated above
energies defined from τγγ(E,z) = 1.

-10
-11

• A spectral shape at around the characteristic EBL-12absorption energy is essentially determined by thespectral shape of EBL.

-13
-14
-15
2

2.5

3

3.5
4
4.5
log(E [GeV])

5

5.5

6

Murase, Dermer, HT, Migliori 2012
1ES 0229+200• The hard spectra of extreme HBLs can be well
reproduced even after strong EBL absorption.

• A lot of >10 TeV photons are required to compensate
the absorption.

Vovk et al. 2012

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201323

Cosmic-ray-induced Cascade
Photomeson production

Bethe-Heitler Pair Creation

E > 6 x 1016 eV for CMB

E > 6 x 1019 eV for CMB

CMB / EBLγpγ~100 Mpc

CMB / EBL
~1 GpcHigher energy photons than EBL attenuation
remain because of e± supply even near observers.

24Gamma rays induced by cosmic rays
Cosmic-ray-induced cascade-7-7

z=0.05
z=0.1
z=0.3
z=0.5
z=0.7

-9

z=0.05
z=0.1
z=0.3
z=0.5
z=0.7

-8
log(E2 FE [GeV cm-2 s-1])-8log(E2 FE [GeV cm-2 s-1])

Gamma-ray-induced cascade

-10
-11
-12
-13
-14

-9
-10
-11
-12
-13
-14

-15

-15
2

2.5

3

3.5
4
4.5
log(E [GeV])

5

5.5

6

2

2.5

3

3.5
4
4.5
log(E [GeV])

5

5.5

6

Murase, Dermer, HT, Migliori 2012

• dN/dE ∝ E-2; 1018 < E < 1019 eV• No IGMF is assumed.

• Gamma-rays with 1019 eV induces the cascades.
• No IGMF is assumed.

Hard spectra are predicted above energies defined from τγγ(E,z) = 1 from cosmic-rayinduced cascade due to the long energy-loss length of Bethe-Heitler pair creation.

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201325

γ-rays from Line-of-sight Cascade• The observed spectra are well reproduced.
• Intergalactic magnetic field reduces γ-ray flux at the
Fermi energy range.

Essey et al. 2011

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
26

SED Modeling of a Extreme HBL

10-11

1ES 0229+200
Liso ~ 1045 erg s-1• Spectral shape is essentially determined by the

10-12• 100 TeV γ-ray emitter can also reproduce theobserved spectrum.

• Diﬀerence between hadronic cascade scenarios

n

-2 -1

nF (erg cm s )spectral shape of EBL.

10-13

10-14
102

and leptonic cascade scenarios appears above 20
TeV

HESS
VERITASE20,low IR
E19,low IR
E19, best fit
E14, low IR
5 hr CTA sensitivity
50 hr
103

• CTA and HAWK have a potential to distinguishthese scenarios.

104

E (GeV)105

Murase, Dermer, HT, Migliori 2012

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201327

Gamma rays induced by cosmic rays
Cosmic-ray-induced cascade-7-7

z=0.05
z=0.1
z=0.3
z=0.5
z=0.7

-9

z=0.05
z=0.1
z=0.3
z=0.5
z=0.7

-8
log(E2 FE [GeV cm-2 s-1])-8log(E2 FE [GeV cm-2 s-1])

Gamma-ray-induced cascade

-10
-11
-12
-13
-14

-9
-10
-11
-12
-13
-14

-15

-15
2

2.5

3

3.5
4
4.5
log(E [GeV])

5

5.5

6

2

2.5

3

3.5
4
4.5
log(E [GeV])

5

5.5

6

Murase, Dermer, HT, Migliori 2012

• dN/dE ∝ E-2; 1018 < E < 1019 eV• No IGMF is assumed.

• Gamma-rays with 1019 eV induces the cascades.
• No IGMF is assumed.

Distant
Hard hard
spectragamma-ray
are predicted
spectrumabove
blazars
energiesmaydefinedresult from cosmic-ray-induced
τγγ(E,z) = 1 from cosmic-raycascades,
inducedwhich
cascadebecomedue toevidence
the longfor
energy-loss
ultra-high-energy
length ofcosmic-ray
Bethe-Heitler
sources.
pair creation.

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 2013
28

List of distant VHE gamma-ray emitters
Fermi sources associated with VHE photons, but not identified by IACTs (z>0.5)
A. Neronov, D.Semikoz, A.M.Taylor and Ie.Vovk: Very-high-energy gamma-ray emission from high-redshift blazars
1
2
3
4
5
6
7
8
9
10
11
12
13

Name
TXS 0138-097
PKS 0426-380
B2 0912+29
Ton 116
PG 1246+586
B3 1307+433
4C +55.17
TXS 1720+102
PKS 1958-179
PKS 2142-75
KUV 00311-1938
RGB J0250+172
PKS 1130+008

RA
25.3576
67.1685138.9683
190.8031
192.0783
197.3563
149.4091
260.6857
300.2379
326.8030
8.393342.6567
173.190067

DEC-9.4788-37.9388
29.5567
36.462258.341343.0849
55.3827
10.2266-17.8160-75.6037-19.3594
17.2067
0.5744

Type
BL
BL
BL
BL
BL
BL
FSRQ
FSRQ
FSRQ
FSRQ
BL
BL
BL

z
0.733
1.11
1.521
1.065
0.847
0.69
0.8955
0.732
0.65
1.139
0.61
1.1
1.223

N30 100
2
13
5
11
9
4
14
0
2
1
11
3
1

N0.1
1f
1f
1f
1b
1b
1f
1b
1f
1b
1f
0
0
0

N0.2
0
0
0
0
0
0
0
0
0
0
2b
1b
1f

Emax
138
134
126
114
104
104
141
168
118
135
152
358
140

L/LMrk421
44.5
151
405
133
67.5
37.5
84.0
46.8
33.5
173
53.2
147
204

P
1.1e-30.9e-30.7e-30.7e-31.2e-30.8e-3
1.6e-3
1.9e-32.3e-3
1.5e-38e-6
7.6e-34.4e-3

Index
2.033
1.946
1.875
1.698
1.949
1.839
Log PB
2.23
2.38
2.517
1.758
1.836
2.178

Table 1. List of high-redshift blazars emitting in the energy band E > 100 GeV. Columns N0.1 and N0.2 give the numbers
Neronov etofal.VHE
2012
photons within an angular distance of 0.1 and 0.2 from the source position. P is the chance coincidence probability for the VHE
photons to be found within the 0.1 or 0.2 circles from the source labels ”f” and ”b” mark photons
pair converted
in thefront(The 1FHL
catalog may
includeand back- layers of the LAT detector. Column N30 100 gives the number of photons associated to more
the sourcein thesourceswithlower
VHE energy
photons.)band 30 100 GeV. Emax is the maximal energy of photon associated to the source. L/L Mrk 421 is the source luminosity in units of
Mrk 421 luminosity at E > 100 GeV.

• They have rather hard spectra.

• The hard spectra motivates possible hadronic origin.

high-energies through absorption on the EBL. The model spec- 3.1.2. PKS 0426-380
trum shown in Fig. 1 is calculated assuming a source redshift of
0.733 and using the EBL model of Franceschini et al. (2008). This bright BL Lac is situated at a redshift of z = 1.11 (Heidt
2004). The source is strongly variable in the GeV energy
The 100-200 GeV Hajime
band source
flux is consistent with the expec- et al.,Takami | CTA workshop 2013 @ ICRR, theUniversityof Tokyo,
Japan,
Sep.
3, 2013
band, see upper
panel ofFig. 2.
Severalactive episodes, during
tation based on the Franceschini et al. model.
which the flux increased by up to an order of magnitude, havebeen observed during the four years of Fermi’s operation.

29

Example: KUV 00311-1938
E2 FE [erg cm-2 s-1]

10-10

KUV 00311-1938

a-induced (low IR)
a-induced (best fit)
CR-induced (low IR)
CR-induced (best fit)Becherini et al. (2012)
H.E.S.S. I

z = 0.61

10-11• Distant hard-source in the Fermi-LAT

10-12• Recently detected by H.E.S.S.

CTA
10-13

• z=0.61 is quoted, but recent optical spectroscopy
indicates only z>0.506.

10-14
10-15 1010Becherini et al. 2012

1011

1012
E [eV]

1013

Pita et al. 2012

1014

HT, Murase, Dermer 2013

Models
EBL: Kneiske et al. (2004) for low and best-fit EBL
Leptonic model• dN/dE ∝ E-s; E > 109.75 eV, Emax = 1014 eV• No suppression from IGMF (10-20 G < B < 10-15 G)• Both models reproduce the Fermi spectrum.

- The sources in the sample except PKS 0426-380
and 2142 are also reproduced.

• These models are distinguishable above ~500 GeV evenconsidering the uncertainty of EBL models.

Hadronic model••dN/dE ∝ E-2.6 exp (-E/Ec); E > 1018 eV, Ec = 1019 eV
No suppression from IGMF (B < 10-14 G for protons)• The hadronic model is favored if z = 0.61 is correct.

- Redshift measurement is important for confirmation.

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201330

Example: KUV 00311-1938 ~ integral flux ~Integral flux is sensitive to the hard component in the hadronic model.

10

-10

a-induced (low IR)
a-induced (best fit)
CR-induced (low IR)
CR-induced (best fit)z = 0.61

10-12
10-13
10

-14

F(>10 GeV) [10-9 cm-2 s-1]

F(>E) [cm-2 s-1]

10-11

10-15 10
10

H.E.S.S. I
2

1

CTA

0
54500 55000 55500 56000 56500
Modified Julian Day

1011

1012
E [eV]

1013

1014
HT, Murase, Dermer 2013

• Integral flux above ~500 GeV can clearly distinguish these two scenarios.
• The light curve (with ~3 month bins) is consistent with constant flux (χ2/d.o.f. = 0.94)
Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201331

Example: PG 1246+586 (z=0.847)

10

-10

a-induced (low IR)
a-induced (best fit)
CR-induced (low IR)
CR-induced (best fit)

10-12
10-13
10-14

F(>10 GeV) [10-9 cm-2 s-1]

F(>E) [cm-2 s-1]

10-11

10-15 10
10

MAGIC II
1CTA
054500 55000 55500 56000 56500
Modified Julian Day

1011

1012
E [eV]

1013

1014
HT, Murase, Dermer 2013

• Even for z~0.85 sources, hadronic origin can be investigated by CTA.
• The light curve (with ~3 month bins) is consistent with constant flux (χ2/d.o.f. = 0.40)
Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201332

According to simulations, the parameters of ejecta, i.e.,−7 c
9 × 10theM
M andβ, depend onthe
theparameters
equation of ofstate
of NSsis
Accordingto simulations,ejecta,i.e.,whichthemallcross smass of
MNSs
maywhichbe larger
M and β, uncertain
depend on[15].
the Theequationof ejecta
state ofis than
4×1
mally achi
10−4M"massup toof∼ejecta
10−2 Mand beβ islarger
distributed
uncertain ∼
[15].
The
M"may
than from'p,−1
4 × 10−20
'p
−4
−2
∼
0.1
to
∼
0.3
for
NS-NS
mergers[15].
The
ejectedmass∼ 10 M" up to ∼ 10 M" and β is distributed from
tons
'p,−1 = 'p /for mergers
BH-NS mergers[27].
A recent
observa∼ 0.1 to ∼may
0.3 beformoreNS-NS[15]. The
ejectedmass−2
tons toξγ /1
th
tion
of
GRB
130603B
implies
M
∼
10
M
and
β
∼
0.1
"
gam
may be more for BH-NS mergers [27]. A recent observa−1
ξγ /10 is
if the post-burst radiation is interpreted
collistion of GRB
130603B implies M ∼ 10−2 M" andasβ a∼macronova.
0.1
ray
When the synchrotron cooling of electrons is dominantgamma
inat t
if the post-burst radiation is interpreted as a macronova.
collisions d
the slow cooling regime, the frequency of the synchrotron
from
SN
1006
When the synchrotron
cooling of electrons is dominant−2/3 −1 inat t =prop
tde
peak νp,syn is scaled according to ∝ M
β (Eq. 21)
the slow cooling regime, the frequency of the synchrotron
frompp
and its flux at ν = ν
is proportional to M s/3 β 3s−3.
arecocpeak νp,syn is scaled accordingp,syn
to ∝ M −2/3 β −1 (Eq. 21)
proportion
Here, we can learn that the flux of NSBMRs
is very senare cs/3 3s−3
and its flux
at
ν
=
ν
is
proportional
to
M
β
.
p,syn
are confine
sitive to β.
neutHere, we can learn that the flux of NSBMRs is very senare cooled
sitive to β.
neutrinos i

Ejecta - ISM Shock from NS Binary Mergers

C.

C.

E [eV]
10

-5

105

1010

` = 0.9` = 0.9, ¡e = 0.3` = 0.9, ¡e = 0.3, d = 10-2
Fiducial
Fermi
Astro-H

10-8
E2 dN/dE [erg cm-2 s-1]

10

0

10-10
10-12
10-14
10-16

Chandra
1010

1015

1020
i [Hz]

1025

CTA

Cosmic-ray acceleration and hadronic
gamma-rays
Cosmic-ray acceleration and hadronic
An analogygamma-rays
with SNRs indicates that a forward shock

W
shoc
X
in NSBMRs can accelerate cosmic rays as well as elec-We in
havetrons.with
TheSNRs
maximum
Lorentzof theshockcosmic rays
An analogy
indicates
thatfactor
a forward
shockstecta
inBamba+
withcantheiratomic number
and nuclear
numberin
A X-rays
at t
in NSBMRs
acceleratecosmicZ
rays
as2003well mass
as elecis estimatedsame
as rayselectrons,The
trons. The
maximumfollowing
Lorentz thefactorof discussion
the cosmic
tectableev
accewith their atomic numberZ and nuclear #mass number A
tdec$1/2 at t = the2 2 2
is estimated following the same
discussion
as electrons,
The deteco
9πZeA
mp β
3ZeβR
B
dec
.
merg
γCR,max = min ,
acceleratio
2
2B
20ξAm
c
10ξσ
m


T$ e
#p
twee
1/2
the observa
2 2 2
9πZeA
m
β
3ZeβR
B
a
dec
p
(27)
.
mergerers
hypγCR,max = min 
,
2
2
tions
10ξσT me B
Here, the 20ξAm
nuclearp cmass is approximately
Amp and m
p
tween
the
W
is the proton mass. Regarded as a function of ξ, theers and th
(27)
ultra
maximum Lorentz factor is numerically represented astions ofSG
Here, the nuclear mass is approximately Amp and mp
ankle
We of
also
is the protonγ mass. =Regarded as a function of ξ, thegaCR,maxultra-high'maximum Lorentz
factor is numerically
represented
aslowe−1/4 −1/4 1/2
3 × 1011 ξ −1/2 Z 1/2 A'B,−2 n0 β0.3 (ξ < ξb,CR )ankle in Ne
th
(28)
1/2
1/3
1/6
2
γCR,max = 1 × 108 ξ −1 ZA−1 'B,−2 M−2 n0 β0.3(ξ ≥ ξb,CR ),of gamma
by th
'
lower
than
−1/4 −1/4 1/2
3 × 1011 ξ −1/2 Z 1/2 A'B,−2 n0
β0.3 (ξ < ξb,CR )Nearby(28)
1/3 1/6 2
8 −1−1 1/2
1 × 10 ξ ZA 'B,−2 M−2 n0 β0.3 (ξ ≥ ξb,CR ),by the Fer

HT, Kyutoku, Ioka 2013

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201333

Summary• The origin of UHECRs are still under debate, although some essential constraints
have been obtained from UHECR and neutrino experiments.

• Towards source identification• Huge statistics above 1020 eV --- JEM-EUSO, TA2, AugerNext, ...
• Multi-messenger approaches --- CTA, IceCube, ARA, ...
• Gamma-ray connection to UHECRs• Hadronic gamma-ray emission• Cosmic-ray-induced cascade• (Inference from physical parameters constrained by leptonic emission)

Hajime Takami | CTA workshop 2013 @ ICRR, the University of Tokyo, Japan, Sep. 3, 201334

35