Diapositive 1

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New insight into Gamma-ray Blazars with the
Fermi-LAT Benoît Lott CEN Bordeaux-Gradignan o
n behalf of the Fermi-LAT collaboration
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Unified Picture of AGNs

• Powered by accretion onto a central, supermassive
  black hole
• Jets highly collimated outflows with ??10
• Large brightness temps, superluminal motion,
  rapid variability in ?-rays
• Unified Model observer line-of-sight determines
  source properties, e.g., radio galaxy vs blazar
• Other factors accretion rate, BH mass and spin,
  host galaxy
• Open questions jet composition, location of
  dissipation, acceleration processes, gamma-ray
  emission processes

Image Credit C.M.Urry P. Padovani
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Blazar classes

from J. Kataoka
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LAT performance
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The flaring and variable sky

• 30 Astronomers telegrams (alert threshold
• FEgt 100 MeV1?10?6 ph cm?2 s?1)
• Discovery of new gamma-ray blazars PKS 1502106,
  PKS 1454-354
• Flares from known gamma-ray blazars 3C454.3, PKS
  1510-089,3C273, AO 0235164, PSK 0208-512, 3C66A,
  PKS 0537-441
• Galactic plane transients J0910-5041, 3EG
  J0903-3531

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Source monitoring
Ex 3C454.3

• EGRET sparse 15-day long viewing periods
• difficult to establish variability
• patterns and determine relevant parameters (duty
  cycle)
• Fermi continuous coverage of all
• sources in the sky

Light curves of some bright sources are
online http//heasarc.gsfc.nasa.gov/W3Browse/ferm
i/fermilasp.html
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Power spectral density
Preliminary
slope-1.70.5
slope-1.20.5
Average PDS for 4 bright FSRQs PKS 0454-234,
3C279 PKS 1502106, PKS 1510-08
Average PDS for 5 bright IBLs/HBLs 3C66,
PKS0447-439, Mrk421, PG 155311, PKS 2155-304
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MW campaigns
3C 454.3 (Lars Fuhrmann)
3C 279 (Masaaki Hayashida)
Interband timing correlation Time resolved SEDs
dynamics of emitting particles ? Location,
environment of emitting zone, acceleration vs
cooling Other campaigns Mrk421, Mrk501,
1ES1959650, 3C66A
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Optical gamma-ray correlation for 3C454.3
Bonning et al. 2009
SMART telescope
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PKS 2155?304 Spectral Energy Distribution

• PKS 2155-304 HBL, z0.116
• First simultaneous
• SED including GeV-TeV data
• Unexpected correlations
• strong correlation between optical and TeV
  fluxes
• X-ray flux varies independently of TeV
• flux
• correlation between
• TeV flux and GeV photon index
• Challenge simple SSC
• models

ATOM
Swift
Fermi
RXTE
HESS
astro-ph 0903-2924
(contact authors B. Giebels J. Chiang)
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Non power-law spectra

• First definitive evidence of a spectral break
  above 100 MeV
• General feature in FSRQs and many LBLs
• Absent in HBLs
• Broken power law model seems to be favored
• ??1.0 gt 0.5 ? not from radiative cooling
• Possible explanations
• intrinsic absorption via ?? opacity from
  accretion disk or BLR photons
• feature in the underlying particle distribution
• Implications for EBL studies and blazar
  contribution to extragalactic diffuse emission

FSRQ
LBL
Preliminary
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LAT Bright AGN Sample (LBAS)
3-month dataset, 10-s significance 106 sources
at bgt0 with high-confidence AGN associations
(CGRaBS/CRATES/BZCat) 2/3 of the sources were not
detected by EGRET 57 FSRQs 42 BLLacs (40)
including 10 HBLs 5 of Unknown type 2 Radio
Galaxies (Cen A, NGC1275)
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Index vs flux
(l,b)(40,80) (40,20)
FSRQ BLLac Uncertain Radio Galaxies
TS100
(l,b)(40,80) Elt 3 GeV
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Photon index distributions
Preliminary
FSRQs
rms 0.19
nFn
n
LBLs
rms 0.15
nFn
Number of sources
IBLs
rms 0.22
nFn
HBLs
rms 0.14
nFn
n
Photon index
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Luminosity Functions

• FSRQs
• Strong cosmological evolution
• More complicated than pure density or pure
  luminosity evolution
• The 3 month LAT AGN sample measures the bright
  end of the luminosity distribution
• BL Lac objects
• No evidence of evolution
• Combined emission from individual blazars in 3
  month sample corresponds to 7 of EGRET
  extragalactic diffuse

L?1.5
L?0.5
L?1.1
(contact M. Ajello)
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detection of NGC 1275

• Classic example of a cooling core cluster
• Voids or bubble seen in the X-ray must be
  inflated by some central source of power, i.e.,
  an AGN
• Variable emission on month to year time scales ?
  AGN Cannot be dark matter or diffuse cluster
  emission
• Inferred blazar luminosity, L??1044-1045 erg s?1,
  is consistent with power needed to inflate the
  voids

• SED fitted with single zone SSC model (solid
  curve) and spine-sheath model (dashed)
• Contact J. Kataoka

COS-B
Fermi
EGRET
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Narrow-Line Quasar PMN J09480022
Optical spectrum of narrow-line Seyfert 1 type
(usually radio quiet). Radio emission is
strongly variable and with flat spectrum -gt
suggests Doppler boosting, now confirmed by LAT.

• First ?-ray detection of such an object
• SED modeling shows this is a typical FSRQ,
  although with a relatively low power.
• Many questions open
• Is this a new type of ?-ray emitting AGN?
• Are there other sources of this type?
• What is the impact of narrow-lines?

(Contact authorL. Foschini)
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Conclusions

• The LAT is providing unprecedented-quality data
  in terms of
• statistical accuracy
• time sampling
• numbers of sources
• opening a new era in blazar science.
• The newly enabled studies
• variability patterns
• spectral features
• time-resolved SEDs, interband timing correlation
• census of blazar populations, evolution
• will undoubtedly yield a better understanding of
  the blazar phenomenon.

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Backup slides
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associations
0FGL 132 sources with TSgt100, bgt10
7 pulsars, 125 AGN candidates
BZCat (Massaro et al. 08) Compilation
of 2500 known blazars association based on
spatial coincidence (Mattox et al.,
01) 102 high-conf. (Pgt90) associations
4 low-conf. (40ltPlt90) associations
CGRaBS (Healey et al. 08) 1627 radio
sources from CRATES association based on
Figure-of-Merit (spatial, radio and X spectrum)
established from EGRET 101 high-conf.
(Pgt90) associations 14 low-conf. (40ltPlt90)
associations
celestial
galactic