Recent Fermi-LAT results on
Active Galactic Nuclei
and future CTA perspectives
Yasuyuki Tanaka
Hiroshima UniversityOutline• Fermi Gamma-ray Space Telescope• New observing strategy• 2013年1月以降に出版されたFermi-AGN関連の結果を主に紹介✓ Fermi Bubble (Akermann+14, ApJ, Cat I)✓ EBL and High redshift blazars✓ TeV FSRQs✓ Radio galaxies: Cen A and M87✓ Extreme HBLs

Large Area Telescope
γPair-conversion telescope

ACDTracker

Si-strip Tracker with tungsten foil converter:
Measure the photon directionCsI Calorimeter: Measure the photon energy,Image the shower
ACD (Plastic scintillator):
Reject charged-particle background•••••Large effective area (9000 cm2 @ 1 GeV,normal incidence)
Large field-of-view (2.4 str)
The entire sky is observed every ~3 hours
Energy range: 20 MeV – 300 GeV
Angular resolution (68% contaminant radius):
0.6 deg @ 1 GeV

e+ eCsI Calorimeter4 x 4 modular array
3000 kg, 650 W

New observing strategy
2013 Dec.~2014 Dec.
(とりあえず1年間)
all-sky survey until 2013 Dec.
exposure map

http://fermi.gsfc.nasa.gov/ssc/proposals/alt_obs/obs_modes.html• 全天サーベイをしながら、銀河中心方向のexposureを増やす
Modified survey modeでの観測が行われている✓ Check for 130 GeV line
✓ Passage of the G2 cloud around Sgr A*

AGN関連のFermi論文数2014
2013
2012
2011
2010
2009
0"

5"

10"

15"

20"

25"

https://www-glast.stanford.edu/cgi-bin/pubpub• 約20本 per year (Category 1, II, IIIの合計)

Outline• Fermi Gamma-ray Space Telescope• New observing strategy• 2013年1月以降に出版されたFermi-AGN関連の結果を主に紹介✓ Fermi Bubble (Akermann+14, ApJ, Cat I)✓ EBL and High redshift blazars✓ TeV FSRQs✓ Radio galaxies: Cen A and M87✓ Extreme HBLs

Fermi Bubble paper by Fermi teamAckermann et al. 2014, ApJ, 793, 64

Spectrum
Cutoff PL with
Γ=1.9+/-0.2
Ecutoff=110+/-50 GeV
L=4.4x1037 erg/s(0.1-500 GeV)
• Different diffuse model• Small bubble area
• Large Gal. Plane mask

(20 deg, instead of 10 deg
utilized here)

Northern and southern bubble spectra

Spectral shape and intensity
agree with each otherNo significant variation of a spectrum
as a function of latitude
NorthSouthMorphologySignificant excess in south-east cocoon,
but no evidence of a jetHadronic model fit

Difficult to reproduce the WMAP+Planck
data points

Leptonic model is favoredOutline• Fermi Gamma-ray Space Telescope• New observing strategy• 2013年1月以降に出版されたFermi-AGN関連の結果を主に紹介✓ Fermi Bubble (Akermann+14, ApJ, Cat I)✓ EBL and High redshift blazars✓ TeV FSRQs✓ Radio galaxies: Cen A and M87✓ Extreme HBLs

ブレーザーBlazars
電波銀河

FSRQ

Radio-loud10%

Radio-quiet
90%

Seyfert(I, II)

HBL

Fossati+98, Kubo+98,
Donato+01• Radio-loud AGN is ~10%
• Synchrotron + Inverse compton (external/synchrotron photons)

Extragalactic Background Lightγγ→e+e-• Level of EBL intensity, which is difficult to measure directly, can be
estimated by absorption feature in sub-TeV~TeV gamma rays

Fermi BL Lac 150天体の統計解析• Statistical anlaysis for 3 redshift bins

(z=0-0.2, 0.2-0.5, 0.5-1.6, 50 objects ineach bin)• Significant detection of absorption
feature caused by EBL• Intrinsic spectral cut-off cannot explain
the observed attenuation featureAckermann+12

Observed gamma-ray opacity is consistent
with minimal level of EBL intensity

Ackermann+12

2 VHE events from z=1.1 blazar PKS 0426-380
Count map of 5-300 GeV
Ultraclean events(0.05° per pixel)

LAT PSF (0.12 deg)for 100 GeV photons
50-100 GeVevents arealso shown

Tanaka+13• 134 GeV and 122 GeV ULTRACLEAN events weredetected from close vicinity of PKS 0426-380

Arrival times ofE>50 GeV ULTRACLEAN events• All of the seven E>50 GeV events were detected duringhigh state of the source

Spectral hardening??
LAT spectrum accumulated
over the ~8 months high state

See also Finke+10,Essey+12, Inoue+13

Γlow=1.91+/-0.04
Γhigh=2.72+/-0.17
EBreak=8.0+/-0.9 GeVTanaka+13

“Gravitationally lensed” blazar
S3 0218+357

http://www.asdc.asi.it/news.php#299• フェルミで検出されている重力レンズブレーザーは
PKS 1830-211とS3 0218+357の2つ

Fermi-LAT light curve of 2012 flare

Cheung+14• Delay of 11.46+/-0.16 days

Bright and hard GeV flarein 2014 JulyDaily PL index was~1.5 in LAT band

MAGIC detection of VHE gamma-raysfrom the z=0.944 blazar S3 0218+357• Most distant VHE emitter to dateOutline• Fermi Gamma-ray Space Telescope• New observing strategy• 2013年1月以降に出版されたFermi-AGN関連の結果を主に紹介✓ Fermi Bubble (Akermann+14, ApJ, Cat I)✓ EBL and High redshift blazars✓ TeV FSRQs✓ Radio galaxies: Cen A and M87✓ Extreme HBLs

Recent results on 3 TeV FSRQs• PKS 1510-089✓ Multiple bright GeV flares in 2011-12✓ Saito+13 (Fermi), Aleksic+14 (MAGIC), Orienti+13 (VLBI)• 3C 279✓ Bright and hard GeV flare in 2013 Dec. (Atel #5680)• 4C 21.35✓ VERITAS detection of steady VHE emission (Atel #5981)

Where is blazar emission zone?

©Marscher• Within BLR (<sub-pc)? or far away (~pc)?
• Seed photons are optical/UV? or IR photons?

MAGIC+Fermi previous result
4C 21.35

Tanaka+11
Aleksic+11• Rapid variability and no spectral cutoff in sub-TeV band
• Compact emission region outside BLR (pc away from
central BH), challenging the standard modelRapid variability in LAT light curve
Daily

Saito+13
Resolved intomultiple flaresDoubling timeof ~1 hour

VLBI follow-up

Aleksic+14• Bright GeV flare occurred at knotejection• Compact emission region at ~pc

away from central BH (as is the caseof 4C 21.35)

TeV and MWL follow-up
in 2012 Feb.
Aleksic+14

knot ejection

Smooth connection
implies single emission
region outside BLRBright and hard GeV flarefrom 3C 279 (ATel #5680)
Fermi-LAT
Public LC

LAT features seem similar to previous
4C 21.35 and PKS 1510-089 cases

2013/12/20=MJD 56646
http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/

VERITAS detection of 4C 21.35
during GeV brighening• The E>100 GeV flux is constant over 10 nights

Outline• Fermi Gamma-ray Space Telescope• New observing strategy• 2013年1月以降に出版されたFermi-AGN関連の結果を主に紹介✓ Fermi Bubble (Akermann+14, ApJ, Cat I)✓ EBL and High redshift blazars✓ TeV FSRQs✓ Radio galaxies: Cen A and M87✓ Extreme HBLs

Radio galaxies• Cen A core (Sahakyan+13)✓ Spectral hardening in GeV band
✓ Constant flux over 4 years (?)• M87 multi-wavelength✓ 10-year MWL monitoring result(Abramowski+12)✓ TeV+VLBI (Hada+14)

Fermi-detected Radio galaxies
NameDistance[Mpc]

FR I or II

TeVCen A

3.7

FR I

Yes (non-variable)

M87

16

FR I

Yes +rapid flares

Fornax A

18

FR I

Cen B

56

FR I

NGC 1275

75

FR I

NGC 6251

106

FR I

3C 78

124

FR I

3C 120142

FR1

BLRG, UFO

3C 111213

FR II

BLRG, UFO

Yes

Cen A core: spectral hardening
2.74+/-0.02
2.12+/-0.14
Ebreak~4 GeV

Abdo+10

Sahakyan+13• Additional component at E>~4 GeV• スペクトルの精密測定 (PL index, cutoff/breakの探査)と変動探索→放射機構の解明

MeV/GeV variability
Flux(E>100 MeV)

No clear evidenceof variability

M87 TeV flares and MWL light curves
TeVFermi-LAT• TeV emission region is locatedat the core or pc-scale knot(HST-1)?

• GeV flux is always steadyduring TeV flare?

Abramowski+12

MWL follow-up ofweak TeV flare in 2012
• After the TeV flare, the radio corebrightened, suggesting that the TeV
photons are emitted at jet base (as is thecase of 2008 flare)• HST-1 flux remains constant and no newcomponent emerged• HE emission is constant before the flare• After the flare, the LAT flux decreased bya factor of ~2 (6-month-bin data)

Hada+14

Spine-layer? (2成分必要)

1. GeVとTeVは別成分
2. X線とTeVが同期して変動 (GeVはX線と同期しないのでspine-layermodelは棄却?)• Snapshot daily monitoring by CTA

Extreme HBLs

Neronov+10• Very faint in GeV band, but finally detected over several-year data accumulation (e.g,Vovk+12, Tanaka+14, Finke+13)• More accurate constraint on IGMF

Summary•••••

Fermi Bubble✓

Cutoff PL with index=1.9 and Ecutoff=110 GeV ✓ No spectral variation over latitude✓

No evidence of a jet✓ Leptonic model is favored

EBL and High redshift blazars✓

Minimum level of EBL model✓

Fermi alert and MAGIC follow-up allowed to detect most distant z=0.944 blazar

TeV FSRQs✓

Far dissipation (pc away from central BH) scenario is favored for PKS 1510 flare in2011 and 2012

Radio galaxies: Cen A and M87✓

Additional component above E~4 GeV, which smoothly connects to TeV data✓

Weak TeV flare in 2012 would take place within 43 GHz core, rather than HST-1Extreme HBLs: Fermi-LAT finally detects GeV counterparts and constraint on IGMF