AGNs with the Fermi-LAT:
What we have seenBenoît Lott
CEN Bordeaux-Gradignan
lott@cenbg.in2p3.fr
on behalf of the Fermi-LAT collaboration“Blazars, other AGNs and GalaxyClusters” Science Working Group

2nd Fermi Symposium 11/09

Benoit Lott

Key questions on blazars• Emission mechanisms (for HE component)– Leptonic (IC of synchrotron or externalphotons) vs hadronic (ππ0→γγγγ,γγ protonsynchrotron)• Emission location– Single zone for all wavebands (completelyconstraining for simplest leptonic models)– Opacity effects and energy-dependent
photospheres• Particle acceleration mechanisms– Shocks, magnetic reconnection, turbulence
acceleration• Jet composition– Poynting flux, leptonic, ions

• FSRQ/BLLac dichotomy• Jet confinement– External pressure, magnetic stresses• Accretion disk—black hole—jet connection• Effect of blazar emission on host galaxies
and galaxy clusters• Blazars as probes of the extragalactic
background light (EBL)
2nd Fermi Symposium 11/09

NASABenoit Lott

Populations

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Benoit Lott

The EGRET legacy~ 100 AGNs
 all radio-loud ~ 97% blazars
 3 radio galaxies: Cen A, NGC 6251, 3C 111
 Mostly FSRQs: FSRQ: 75% BL Lac: 25%
 Mostly (> 90%) low-energy peaked blazars (synchrotron peak in opt/UV) 13 blazars in first AGILE catalog
2nd Fermi Symposium 11/09

Benoit Lott

The LAT Bright AGN Sample (LBAS)• 3-month dataset, TS>100• 132 0FGL (Bright Source List) sources at |b|>0°• 116 AGN associations with
•CGRaBS-CRATES(Healey+ 08)•BZCat (Massaro+ 08)• 106 high-confidenceassociations:• 58 FSRQs• 42 BLLacs (40%)
10 HSPs• 2 Radio Galaxies
Cen A, NGC1275• 4 of Unknown type
Abdo A. A. et al. 2009 ApJ 700, 597
EGRET sources: only 30%

2nd Fermi Symposium 11/09

Benoit Lott

The First LAT AGN catalog (1LAC)• 11 month data setPreliminary• 1079 TS>25, |b|>10°sources• 668 AGNs (Passoc>80%)+186 candidates• Census:• 286 FSRQs• 284 BLLacs(141 with measured z)• 69 of unknown type• ~10 Radio galaxies

Differences between Northern Hemisphere andSouthern one (FSRQs: 7%, BLLACs: 25 %)2nd Fermi Symposium 11/09

Posters: P5-188,S. Healey et al.
P1-37,M. Shaw et al.

Benoit Lott

Photon index – Flux distributions
Preliminary
3EG flux limit

Poster P5-188, S. Healey et al.
2nd Fermi Symposium 11/09

Benoit Lott

Redshift distributions
Preliminary

Poster P5-188,
S. Healey et al.
2nd Fermi Symposium 11/09

Benoit Lott

Population studies• Log N- Log S presents a flattening aroundF[E>100 MeV]=6.7 x10-8 ph cm-2s-1• FSRQ densities peak at a redshift which
increases with increasing luminosity(i.e. LDDE behavior)
M. Ajello’s talkPr

2nd Fermi Symposium 11/09

naimeliry

Benoit LottSpectral properties
in the γ-ray band

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Benoit Lott

SED-based classification
P. Giommi’s talk, Posters P5-188, 1-29, S.Cutini et al.
• Simultaneous Swift data enabled thedetermination of νsyn for 48 LBAS
sources• Calibration of relation with νsynestimated from αox, αro• subclasses assigned from νsynLSP, ISP, HSP: low-, intermediate-,
high-synchrotron peaked blazars,resp.
• LSP: log(ννsyn ) < 14• ISP: 14<log(ννsyn ) < 15
• HSP: log(ννsyn ) > 15with νsyn in Hz

2nd Fermi Symposium 11/09

Preliminary

Benoit LottPhoton index distributions in LBAS
Preliminary

FSRQs
rms: 0.19(Poster P1-21, L. Escande et al.)Photon index determined with the first
6-month data set
LAT range
FSRQs
HSP-BLLacs
LSP-BLLacs
ISP-BLLacs
ISP-BLLacs
rms: 0.22

ν
νFν
Fν
ν

Number of sources

LSP-BLLacs
rms: 0.15

ν
HSP-BLLacs
rms: 0.14

2nd Fermi Symposium 11/09

Photon index• Strong correlation between photon index
and blazar class• Narrow distributions point to a small
numbers of parameters driving the blazarSEDs
Benoit Lott

Photon index vs νsyn, Lγγ, redshift
FSRQs
LSP-BLLacs
ISP-BLLacs
HSP-BLLacs• All (but one) FSRQs in 1LAC
are LPBs• Most BLLacs are HSPs
these correlations enable the« blazar sequence » concept tobe revisited but beware oflimitations!

Preliminary

2nd Fermi Symposium 11/09

FSRQs
BLLac - LPBs
BLLac - IPBs
BLLac – HPBs
Benoit LottRadio Galaxies

Relative constancy of photon index(Poster P1-21, L. Escande et al.)Preliminary
daily l.c.

weekly l.c.

daily l.c.

« Harder when brighter » effects observed
but moderate variations (∆Γ∆Γ <0.3) seem tobe the rule
Process stabilizing the spectral shape?
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Benoit Lott

Non-power law spectra• General feature in FSRQs
and many LSP-BLLacs• Absent in HSP-BLLacs• Broken power law modelseems to be favored• ∆Γ~1.0> 0.5 → not from∆Γradiative cooling• Possible explanations:

FSRQ

LSP-BLLacPreliminary– feature in the underlying
particle distribution– Klein-Nishina effect– γ−γ absorption effect• Implications for EBL
studies and blazar
contribution toextragalactic diffuseemission

2nd Fermi Symposium 11/09

Challenge for modelers LSP-BLLacs
to FSRQs
account for the break
HSB-BLLacs
ISP-BLLacs
and the relative constancy of spectral index with time
Benoit LottTemporal properties
in the γ-ray band

2nd Fermi Symposium 11/09

Benoit Lott

The variable sky~50 Astronomers telegrams(alert threshold:F[E>100 MeV]~10−6 ph cm−2 s−1)
• Discovery of new gamma-ray blazars:
PKS 1502+106, PKS 1454-354• Flares from known gamma-ray blazars:
3C454.3, PKS 1510-089,3C273, AO
0235+164, PSK 0208-512, 3C66A, PKS
0537-441• Galactic plane transients: J0910-5041,
3EG J0903-3531

Flare Advocates issue alerts
and feed the Fermi blog
Poster P5-203, S. Ciprini et al.

2nd Fermi Symposium 11/09

Benoit Lott

Power Density Spectrum• 1/f−α with α between 1 (« flicker », « pink-noise ») and 2 (« shot noise », «Brownian»)with peak around 1.6-1.7 (similar to optical or radio)•Caveat: weekly and 3-day bin light curves; mid- long-term temporal behavior
investigated so far

Poster P1-27,S. Ciprini et al.
9 brightest FSRQs
α =-1.5±0.2

Preliminary

bright 9 FSRQs α =-1.5±0.2
faint 13 FSRQs α =-1.6±0.3
bright 6 BLLacs α =-1.9±0.4

No significant difference in PDS shape between BLLacs and FSRQs but a tendency
for the former to be slightly steeper. BLLacs have also a lower fractional variability.
2nd Fermi Symposium 11/09Benoit Lott

Multi-frequency studies

MW opportunities:
Poster P5-199, D. Thompson
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Benoit Lott

Multiwavelength data for PKS1502+106• first blazar discovered by Fermi• luminous FSRQ at z=1.839• strong correlations between
γ-ray and other bands: optical,X-ray• SED well reproduced by EC+SSCmodels

correlated variability

Time-resolved SEDs

• strong correlated variability indicates co-spatiality of emission• leads/lags shed light into electron dynamics/geometry
Preliminary
seeS.
Wagner’stalk,SMARTS
posterP1-39
Many
other
examples,Poster
P1-26,S.
Ciprinietal.
2 Fermi Symposium 11/09
Benoit Lottnd

Multi-wavelength campaign on 3C279• Bright FSRQ, z=0.536

Preliminary• Intensive Multiwavelength Campaign~300 d• Coincidence of γ-ray flare and change
in optical polarization (KANATA)• Drop from 30% to 5%• EVPA changes by 208°
• Orphan X-ray flare detected• Polarization event lasts 20 days
• Co-spatiality of γ-ray and optical emissions• Non-axisymmetric structure of the emissionzone• Curved trajectory along the jet• revent>105 Schwarzschild radii

M. Hayashida’s talk2nd Fermi Symposium 11/09

Benoit Lott

The GeV-TeV connection
MW campaigns on– Mkn421, Mkn501, 1ES 1959+650 (Poster P1-53, D. Paneque et al.,P1-17, A. Konopelko et al.)
– PKS 2155-304 (Poster P1-24, D. Sanchez et al.)– 3C 66A (w. Veritas)– PKS 1424+240 (w. Veritas, poster P1-15, A. Furniss et al.)– RGB J0710+591 (w. Veritas, poster P1-30, P.Fortin et al.)
– PKS2005-489 (w. HESS, poster P1-35, S. Kaufmann et al.)and more….
Enormous set of data!

2nd Fermi Symposium 11/09

Benoit Lott

MW campaign on PKS 2155−−304 (with HESS)HSP-BLLac, z=0.116
nonflaring,low/quiescentstate
First simultaneous
SED including GeVTeV
Unexpected
correlations:• strong correlation
between optical and
TeV fluxes• X-ray flux varies
independently of TeVflux• correlation between
X-ray flux and GeV
photon index
Challenge simple SSC
models
2nd Fermi Symposium 11/09

ATOM

SwiftFermi
RXTEHESS

Aharonian, F. et al. 2009, ApJL, 696 L150
contact authors: B. Giebels & J. Chiang
Benoit Lott

MW campaign on Mrk421• 4.5 months long (Jan 20th – June 1st , 2009)• ~20 instruments participated covering frequencies from radio to TeV• 2-day sampling at at optical/X-ray and TeV (when possible: breaks due to moon,weather…)

Most complete SED
collected for Mrk421
until nowFirst time that thehigh energy bump is
resolved without
gaps from 0.1 GeV toalmost 10 TeV

Poster P1-53, D. Panequeet al.

Preliminary
2nd Fermi Symposium 11/09

Benoit Lott

The GeV-TeV connection
21/28 TeV AGNs detected by Fermi-LAT (5.5 months of data), now 25/30• mostly BLLacs, mostly HSPs
•2 RGs: Centaurus A, M87
arXiv:0910.4881 (Poster P1-18 S. Fegan et al.)Most of the bright TeV blazars have been in low states since Fermi launched.
Low variability in the GeV range.
Search for new TeV emitters (poster P5-190, P. Fortin et al.)
2nd Fermi Symposium 11/09

Benoit Lott

Difference between GeV-TeV photon indices vs redshift∆Γmax=2.5for PG1553+113
no measured z(poster P1-20,D. Horan et al.)Warning: non-simultaneous data!
Poster P1-18, S. Fegan et al.
2nd Fermi Symposium 11/09

Benoit LottRadio- γ-ray connection
Investigation of correlations between
γ-ray and radio correlated variability
γ-ray and radio luminosities
γ-ray luminosity and jet properties
γ-ray flares and ejection of new
radio components

OVRO
OVRO

Poster M. Giroletti

Preliminary

MOJAVE

Poster Chin-Shin Chang

PosterM. Kadler

Effelsberg &Poster L. Fuhrmann
Poster W. MaxMoerbec

OVRO
Poster S. Ciprini

see A. Marscher’s & M. Lister’stalks
2nd Fermi Symposium 11/09

Benoit LottNon-blazar sources

2nd Fermi Symposium 11/09

Benoit Lott

Radio (non-blazar) Galaxies•Cen A (Poster P1-14, J. Finke et al.)– nearest radio galaxy, FRI, D=3.7 Mpc, seen by EGRETand HESS
– Fermi-LAT detection. Γ: 2.71 ± 0.09, TS=318– two-zone SSC model required to reproduce whole SED•M 87 (Poster P1-49, W. McConville et al.)– giant radio galaxy, FR1, D=16Mpc– detected by HESS, VERITAS, MAGIC– Γ : 2.26 ± 0.13, F8: 2.45 ± 0.6, TS=108– No indication of variability over 11 months– good fit of SED with one-zone SSC (e from sub-pc core)•NGC 1275 (Poster P1-33, J. Kataoka et al.)––––“cooling core” cluster
detected by COS-B, not by EGRETLAT flux 6x larger than EGRET upper limit« short-term» variability points to an AGN+ 7 other radio galaxies (E.Cavazzuti’s talk)2nd Fermi Symposium 11/09

Benoit Lott

Radio (non-blazar) Galaxies
Other class?
• PMN J0948+0022, Narrow-line, radio loud Sy1 (contact: L. Foschini)– SED similar to FSRQ, less powerful– Radio emission is strongly variable and with flat spectrum, suggests
Doppler boosting, now confirmed by LAT– More similar sources detected

Abdo, A. A. et al. 2009, ApJ, 699, 976

Limits on Galaxy clusters
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Benoit Lott

Extragalactic Background Light

2nd Fermi Symposium 11/09

Benoit Lott

Extragalactic Background Light (EBL)• LAT-detected blazars at high z havesoft spectra, many exhibiting breaks

Preliminary• Little-constraining results provided
by initially planned method based onratio• However, highest-energy photons fromdistant blazars rule out models thatpredict the highest opacities.

See L. Reyes’ talk2nd Fermi Symposium 11/09

Benoit Lott

Summary Fermi has discovered hundreds of new sources, proving that blazars dominate
the extragalactic sky : BLLacs (x~20 wrt EGRET), many being HSPs
 FSRQs (x~5 wrt EGRET) majority of TeV AGNs.
making detailed population studies possible.
 Important spectral properties (correlation of photon index with blazar class, spectral
breaks, relative constancy of photon index with flux) have been observed.
 Variability time scales were observed ranging from sub-day to several months.
 Many multifrequency studies heve been triggered by Fermi observations, providing
time-resolved SEDs and interband (radio, optical, X-ray, TeV) temporal correlation.
 The emission of gamma-rays from the lobes of Cen A has been discovered.
 Many new non-blazars sources have been detected (Radio galaxies, NRLSy1, Cen A
giant radio lobes).
 Constraints on EBL opacity have been obtained.
A lot of novel features and correlations to digest, but ultimately a better understanding of
gamma-ray emitting AGNs will emerge.
2nd Fermi Symposium 11/09

Benoit Lott