Do blazars have additional
spectral components in theTeV band?
Yoshiyuki Inoue(JAXA ITY Fellow)
Yasuyuki T. Tanaka, Shuji Matsuura, Koji Tsumura
ASJ meeting, Kobe, 2015-09-09

Gamma-ray Attenuation by
Cosmic Optical & Infrared Background© MPI

Spectral hardening at the TeV band?

Astrophysical Journal, 768:197 (17pp), 2013 May 10

10Inoue et al.

PKS 0426-380 @ z = 1.1
The most distant VHE blazar– 21 –-9-10

10H 2356-309
z = 0.165

RX J0648.7+1516
z = 0.179

1ES 1218+304
z = 0.182

1ES 1101-232z = 0.186-1110-910-1210Observed
EBL corrected (Franceschini et al. 2008)
EBL corrected (Inoue et al. 2013)
Broken PL model-10101ES 0347-121
z = 0.188

RBS 0413
z = 0.19

1ES 1011+496
z = 0.212

1ES 0414+009
z = 0.287-2 -1

10-910E dN/dE [erg cm s ]-1110-1210-1310-910-1010222E dN/dE [TeV/cm /s]-13-1010-1110-1110-1210-1310S5 0716+714
z = 0.31
0.1

1Energy [TeV]

4C+21.35
z = 0.432
10 0.13C 66Az = 0.444
1Energy [TeV]

10 0.1

3C 279z = 0.5362
1

Energy [TeV]

10 0.10.1

110Energy [TeV]1

10Energy [GeV]100

Tanaka, YI, +’13

YI+‘13are 14. Same as Figure 13, but for sources at z > 0.15. References for the data are H 2356-309 (Aharonian et al. 2006b), RX J0648.7+1516 (Aliu et al. 2011),
Fig. 4.— SED of PKS 0426−380 derived from the Fermi -LAT data accumulated during the1218+304 (Acciari et al. 2009b), 1ES 1101−232 (Aharonian et al. 2007c), 1ES 0347−121 (Aharonian et al. 2007a), RBS 0413 (Aliu et al. 2012), 1ES 1011+496
ert et al. 2007b), 1ES 0414+009 (Abramowski et al. 2012a), S5 0716+714 (Anderhub et al. 2009), 4C+21.35 (Aleksić et al. 2011a), 3C 66A (Aleksić etmostal. 2011b),
energetic flaring state spanning MET 280000000 (17:46:38 UT on 2009 November 15)
C 279 (Albert et al. 2008).
to 302000000 (08:53:18 UT on 2010 July 28; see also the black horizontal line in Figure 2).
olor version of this figure is available in the online journal.)• Spectra of TeV blazars seem to show
hardening.
The observed spectrum is denoted by black squares and the highest energy bin is a 95%

der spectra above several hundred GeV (see also Finke et al.
0).
o explain such intrinsically hard spectra, some authors have
ntly suggested secondary cascade components generated
very high energy cosmic-rays or gamma-rays, which may
offer a probe of intergalactic magnetic fields (e.g., Essey
Kusenko 2010; Essey et al. 2011; Essey & Kusenko 2012;

model of hierarchical galaxy formation, into which Pop-III stars
were incorporated in a simplified fashion. Our baselineconfidence
model is level upper limit. The spectra corrected for the EBL-related attenuation, usingconsistent with a wide variety of observational data forthe
galaxies
EBL models of Franceschini et al. (2008) and Inoue et al. (2013), are represented by
below z ∼ 6 (Nagashima & Yoshii 2004; Kobayashi et al. 2007,redz <circles2010), and is also capable of reionizing the universe by
8. and blue triangles, respectively. A broken power-law model which maximizes theHowever, in order to account for the Thomson scattering
optical for the 0.1–300 GeV Fermi -LAT data is also indicated with black dashed line.
likelihood
depth measured by WMAP, the ionizing photon emissivity is• It is also known that Cen A has a new spectral component at TeV.

What is the origin of the hardening?

TheJuly
AstrophysicalJournal, 740:64 (9pp), 2011 October 20
Lefa, R
The AstrophysicalJournalLetters, 771:L32 (5pp), 201310
Takami, Murase, & Dermer
KUV
00311-1938(z=0.61)
1ES 0229+200 (z=0.1396)
1ES 0229+200 (z=0.1396)-10
SecondaryGammaRaysStochastic
Acc.
10γ-induced (low IR)-10-9.5

1010-13-11.5-14-1410-1210-15
101010111210E [eV]1013-15141010-12.5

Takami+’131410Fv ∝ v 1/3-11

H.E.S.S. I-2 -1-13-1210Fv ∝ v 1/3

10CTA-10.5

2F(>10 GeV) [10-9 cm s ]10-123

10-11E Exp[-E/Ec]

F(>E) [cm s ]-112

γ-induced (low IR)
γ-induced(best fit)
H.E.S.S. lowlevel EBL(low IR)
H.E.S.S.CR-inducedhigh level EBL
CR-induced(bestfit)SWIFTE Exp[-(E/Ec) ]-10210γ-induced (best fit)
CR-induced (low IR)
CR-induced (best fit)Becherini et al. (2012)
H.E.S.S. I

log vFv [erg.sec.cm]-2 -1-1

E2 FE [erg cm-2 s ]1021CTA054500 55000 55500 56000 56500
Modified Julian Day

10 16

10181120122210log v [Hz]E [eV]

241310 26

Lefa+’1110
2814

10. Hard spectrum blazar 1ES 0229+200 at z = 0.139 with SED modeled within an SSC approach using Maxwellian-type electron distribFigure 1. SEDs calculated for gamma-ray-induced (red) andFigure
UHECR-inducedusedaretheIRsameas in Figure 3. Datapoints2.
shownin the figure
from Zacharopouloutoet al.
whereintheFigure
intrinsic (de-absorbed)
FigureIntegral
fluxarecorresponding
the(2011),SEDs
1 (KUV sou(blue) cascade scenarios for KUV 00311−1938 (z = 0.61) using
low(thick)derived based on the EBL model of Franceschini et al. (2008) with (1) EBL level as in their original paper (“low-level EBL”) and (2) (maximum00311−1938) with the H.E.S.S.
sensitivity(presentedEssey+’11,
by Y. Becherini
theofanalyzed• and best fit (thin) EBL models deduced by Kneiske et al. (2004)bywith(Essey I&integral
Kusenko’10, Essey+’10,a factor
1.6 (“high-level EBL”).
in Rencontres de Moriond 2009; http://moriond.in2p3.fr/J09/) and the integral
LAT data (green) with a H.E.S.S. preliminary spectrum (magenta;Becherini(A color versionof this figure is available in the online journal.)
sensitivity goal of CTA for a 50 hr observation (Actis et al. 2011). The inset
etMurase+’12,al. 2012). WeTakami+’13,
take s = 1.76.YI+‘14b)
The isotropic equivalent energy of input gamma
shows a >10 GeV light curve with 16 equal time bins, each lasting 90.3 days.
rays for the gamma-ray-induced cascade Liso
source protons forγ and of UHECRthe
Derishev, E. V., Aharonian, F. A., Kocharovsky,
V. V., &high low-energy cutoffs
neededin leptonic
synchrotronThelight curveis consistent
with a constantfluxhypothesis
with χr2 = 0.95
iso46−147−1
2003,
Phys.
Rev.
D,
68,043003
ergs , rea UHECR-induced cascade Lp are 3.5×10 erg s and 1.1×10
Comptonmodelsfor the hard
spectrumsources.only from finite flux points.
which
is calculatedDermer, C. D., & Schlickeiser, R. 1993, ApJ, 416, 458
spectively.
The
differential
sensitivity
curve
for
a50
hr
observation
with
H.E.S.S.
Althoughourmainpurposehere
isnotto fit data, Figure 10•
Essey, W., Kalashev, O., Kusenko, A., & Beacom, J. F. 2(A color
versionof this figure
is available
in the online journal.)
I (http://www.mpi-hd.mpg.de/hfm/HESS/pages/home/proposals/;line),showsdashedthat a Maxwellian-type
electrondistribution
could also
Franceschini, A., Rodigliero, G., & Vaccari, M. 2008, AFritz, K. D. 1989, A&A, 214, 14
provide(CTA;a satisfactory
and the 50 hr sensitivity goal of the Cherenkov Telescope Array
Actis explanation for the hard TeV component
Georganopoulos, M., Kirk, J. G., & Mastichiadis, A. 200
in 1ESet al. 2011; dotted line) are also plotted. The flux lower thanthe0229+200.
sensitivity-10
Giebels, B., Dubus, G., & Khélifi, B. 2007, A&A, 462, 2
Our results
illustrate that even within
10 a leptonic synchrotroncurve can be achieved under a relaxed criterion of wider energy-binsand lower
Gould, R. J., & Schréder, G. P. 1967, Phys. Rev., 155, 14
γ-induced(lowIR) ApJ, 383, L7
Comptonapproachrelatively
hard
intrinsic TeV source spectra
Henri,G., & Pelletier,G. 1991,
significance required to estimate flux in each bin.
γ-induced(bestfit)6, 317
may be encountered under a variety of conditions. While thisKardashev,
N. S. 1962,SvA,(A color version of this figure is available in the online journal.)
CR-induced(low IR)
Katarzyński,K., Ghisellini,G., Tavecchio, F., Gracia, J.,
may be reassuring, the possibility10of-11having such hard source•MNRAS,
368,
L52(Stawarz & Petrosian’08,Lefa+’11).
CR-induced(bestfit)
spectra within “standard models” unfortunately constrains theKifune, T. 1999, ApJ, 518, L21
potential of extracting limits on the EBL density based on γ -ray
Krawczynski, H., Coppi, C. S., & Aharonian, F. 2002, M
observationsof blazars, one of the hot-12
topics currently discussed
Longair, M. S. 1981, High Energy Astrophysics (Creproduced by both gamma-ray- and UHECR-induced
cascade10 instruments.
University Press)
inthecontextofnextgeneration
VHE•(Cerutti+’14).

Secondary gamma rays from cosmic rays along line of sight.

Observed GeV-TeV photon index dependence on redshift will be diﬀerent from
simple CIB attenuation. There should also be additional spectral components in theTeV band.

-2 -1) [cm s ]Stochastic acceleration]

Lepto-hadronicemissionscenarios
between 10 and100 GeV. The UHECR-induced cascade predicts larger flux above 200 GeV and harder
spectrumWe thankS. Kelner and S. Wagner for helpful discussions.

Maraschi, L., Ghisellini, G., & Celotti, A. 1992, ApJ, 39
Medvedev, M. V. 2006, ApJ, 637, 869

TeV blazar sample
E2dN/dE [TeV/cm2/s]

10-7
10-8
10-9-10
10
10-11
10-12
10-13-7
10
10-8
10-9
10-10-11
10
10-12
10-13-7
10
10-8
10-9
10-10
10-11
10-12-13
10

1ES 1215+303
z = 0.130

1ES 0806-524
z = 0.138

1ES 0229+200
z = 0.14• Select 36 blazars with z

from the default TeVcat
catalog.
• Low-state data are

1RXS J101015.9 - 311909 H 2356-309
z = 0.142639
z = 0.165

RX J0648.7+1516
z = 0.179

available for 31/36.
• 3FGL SED data.

1ES 1218+304
z = 0.182

1ES 1101-232
z = 0.186

1ES 0347-121
z = 0.188• CIB correction by YI+’13.
• Systematic parameter

study w/ MWL data is
YI & Tanaka in prep. also on-going.

10-4 10-3 10-2 10-1 100 10110-4 10-3 10-2 10-1 100 10110-4 10-3 10-2 10-1 100 101
Energy [TeV]
Energy [TeV]
Energy [TeV]GeV-TeV index dependence on redshift

The Astrophysical Journal Letters, 751:L11 (4pp), 2012 May 20

Essey & Kusenko

32.56KTeV-GeV

∆Γ

2
1.5
1
0.5
0

Obviously, for a sufficiently distant source, secondary gamma
rays5 must dominate because they do not sufferVHE
fromBlazars
exponential
Essey
andpredicted
Kusenko’12 (z>0.1)
suppression as in Equation(2). The
spectrumof γ -rays
Inoue et al. ’13turns
4 out to be similar for all the distant AGNs. Essey & Kusenko(2010) and Essey et al. (2010, 2011b) have calculated the spectra
for redshifts of 3C279, 1ES 1101-232, 3C66A, 1ES0229+200,
3and several other blazars, all of which yield a remarkably good(one-parameter) fit to the data (Essey & Kusenko 2010; Essey
2 2010, 2011b).
et al.
Based on our numerical results using a Monte Carlo propagation
code described by Essey & Kusenko (2010) and Essey
1et al. (2010, 2011b), we find that the spectra have a weak redshift
1ESfor0229+200
dependence and, in the TeV energy range,
0.2 " z " 0.6, it
can0be approximated by the following simple relation:

00.2

0.4

0.6

0.8

1

1.2

1.4

00.1z Essey & Kusenko ’12

0.2
0.3+ αz, zΓTeV ≃ ΓpRedshift

0.4

YI+
(5) in prep.

Figure 1. Spectral change, ∆Γ = ΓTeV − ΓGeV , for TeV detected blazars
where Γp is a constantand α ≈ 1. scenario.
observedby Fermi.
Dataclear
points fromthe Fermi Second
catalog (The Fermi-the secondary• thereis nosignature
supportinggamma-ray
Let us now consider a flux of TeV gamma rays which is theLAT Collaboration 2011) were separated into three sets: nearby sources (redinverted triangles), intermediate sources (green triangles), and distant sources
sum of two components that have the above-mentioned scaling• no significant(blue diamonds).
The lines are the best
fits to Equation (10)D = 17.46
correlation
forwithz>0.1.
with distance:(dashed line) and (Γp − Γs ) = 0.995 (solid line).
(A color version of this figure is available in the online journal.)
1−(Γs +DH0 d)• But, 1ES 0229+200 seems to be peculiar.

FTeV = F1

d20.5exp(−d/λγ ) Eeffect would increase ∆Γ because the variation implies some ad1 via F-test.
−d/λγ −(ΓNod)
p +αH0sources• additional components at TeV band are not significantly+seen
F(1−e)E(6)2 2ditional softening due to moving past the Compton peak, whichdwithP(F)<0.05.
is notsupportedby the data. TeV spectra, if they are secondary

Cosmic TeV Gamma-ray Background-31
1010Total CGB (Fermi)
Total
Resolved CGB (Fermi)
Resolved CGB
VHE (Fermi)
Blazars
UpperVHE
LimitBlazars(II12)
Upper Limit(II12)
Mrk
421
IceCube (i perMrkflavour)
501
AMS (e++e-)

E2 dN/dE [MeV2/cm2/s/sr/MeV]

01010-4-1
10-2
10-5
1010-310-6
10-4-510-7
1010-6-810 -7
10103

441010105105 106 106 107 107108
Photon Energy [MeV]

8910101091010

YI & Tanaka in prep.

• These TeV data give lower limit on to the cosmic gamma-ray background.
• Current limit at 0.3-10 TeV is✓◆ 1✓◆ 0.7
EE
522 dN53 ⇥ 10
[MeV/cm /s/sr] < E[MeV/cm2 /s/sr]< 5 ⇥ 10100GeVdE100GeV• Fermi has resolved more portion of the TeV sky than IACTs do?

• Need to remove ~3 orders higher electron background to detect the CGB with CTA.

Summary• We use 31 TeV blazar samples from TeVcat together withthe Fermi 3FGL data.
• GeV - TeV index distribution has no correlation and no

significant evidence for the secondary gamma-ray scenario• Resolved cosmic TeV gamma-ray background fluxes byIACTs is lower than that resolved by Fermi.
• To measure the cosmic TeV gamma-ray background, CTA

needs to remove ~3 orders of magnitude higher electron
background.