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Transcript
Gamma-ray (Fermi-LAT)
properties of microwave
selected AGNs
E. Cavazzuti, D. Gasparrini, P. Giommi,
C. Pittori, S. Colafrancesco
and
On behalf of the Fermi-LAT collaboration
The Extreme Sky 2009: sampling the Universe
above 10 KeV
Otranto, 13 October 2009
Blazars







less than 5% of the whole AGN class

in the gamma rays, they are the most
beamed (jet at  20-30°)
broad band non thermal continuum, L~1049 erg s-1
compact morphology (core flux >> extended flux)
flat spectrum (radio spectral index r  0.5)
rapid variability (large L/ t)
high and variable optical polarization
abundant component within the high galactic
latitude population of sources.
Unification Model
(Urry & Padovani 1995):
Same Engine, Different Points of
View
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Blazar Spectral Energy Distributions
Inverse Compton
Synchroton Radiation
__ Low Peaked Blazar
--- High Peaked Blazar
Radio wave
Visible
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
X-Rays
rays
TeV
Broad band emission
Open Questions
 Emission models:
 Homogeneous Synchrotron Self Compton, External Compton,
Multiple SSC components?
 Different emitting regions?
 Acceleration mechanisms
 Variability
 Duty cycle
We investigate these problematics using a multi-wavelength approach
through WMAP (-wave) and Fermi (-ray) observations.
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Strategy
 Build a complete sample of blazars selected in the microwave
band, starting from the WMAP bright source catalogues
 Study the properties of this microwave selected sample of jetdominated AGN looking for:
– synchrotron peak distribution
– gamma-ray spectral index
– possible relations between -wave fluxes and X-ray, -ray:
duty cycle, , …
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Cosmic Microwave Background Radiation
 Primordial photons redshifted to microwave frequency due to the Universe
expansion
 We see these photons as cosmic background in microwave band
 Tiny inhomogeneities in the early universe left their imprint on the CMB in the
form of small anisotropies in its temperature
 These anisotropies contain information about basic cosmological parameters (e.g.
total energy density and curvature of the universe)
but between us and CMB there are some foreground sources with
microwave emission
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
WMAP (Wilkinson Microwave Anisotropy Probe)
Measurement the temperature differences in the Cosmic Microwave Background
(CMB) radiation at five frequencies (23, 33, 41, 61,94 GHz)
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
The ox - ro diagram: WMAP bright sources
(Massaro et al. 2009,
A&A, 495, 691)
sample peaked around
typical blazar values
Radio loud
Radio quite
•
•
•
•
•
•
242 FSRQs
40 BL Lacs
33 Radio galaxies
14 Steep Spectrum QSOs
3 starburst galaxies
3 planetary nebule
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
•
•
•
19 candidate blazar
27 unidentified
5 other types
TOT 390
(Giommi et al. 2009,
astro-ph 0908.0652v1)
The vast majority of bright WMAP
foreground sources are blazars
-wave to X-ray correlation: WMAP - Swift




establish the X-ray properties of a statistically
representative
IC emission
evidence
sample of -wave selected blazars
no X quiet
population
verify or exclude the existence of a population
of X-ray
quiet blazars
compare the X-ray properties of these sources with those of blazars
compatible with GHz selected LBL
selected in different energy bands
complete the X-ray measurements of a -wave
flux-limited
sample of
tight WMAP
x distribution
blazars, useful for multi- statistical studies
Fx good estimator for wave emission
(Giommi et al 2007,A&A,468,571)
1Jy2227-088=WMAP024
1Jy1548+056=WMAP007
3C395=WMAP034
1Jy1406-07=WMAP203
1Jy0805-077=WMAP133
simultaneous data are shown with same symbol
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Fermi-LAT Bright AGN source list
 132/205 with |b| > 10 (7 pulsars, 14 unid)
• 111/125 are bright, flat spectrum radio sources
• 98/111 have optical classifications, 89/111 have redshifts
• CRATES (all-sky radio catalog), CGRaBS (all-sky optical spectra), BZCAT
• 34% BL Lac fraction (vs 19% for EGRET)
(Abdo et al. 2009, ApJ, 700, 597)
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Gamma-ray properties of WMAP balzars
Inverse
Compto
n
Synchroton
Radiation
Preliminary
__ Low Peaked Blazar
--- High Peaked Blazar
Radio wave
Visible
X-Rays
rays
TeV
The distribution of spectral index confirms the selection of Low Peaked Blazars
in the microwave band
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
 and Duty Cycle
(Giommi et al. 2006A&A,445, 843G, Pittori et al. Ap&SS. 309, 89P 2007, Cavazzuti et al. AIPC 921, 246C
2007)
Define a -wave to -ray index:
   
log f  (94GHz) / f (100MeV )
log(   /  )
Limiting value: ()100%CGB=0.994
This is the value of an hypotetical source
that would produce 100% of the CGB if

representative of the class. Any source
with  < 0.994 shoud have a duty cycle
lower than 100% in order not to
overproduce the extragalactic diffuse ray background.

Duty Cycle 
100
11.41(0.994  )
10
Duty cycle > 100% => source
where: log (  (94 GHz) /  (100 MeV ))  11.41 always visible (also in low state)
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
-wave to -ray correlation: WMAP - Fermi
UNKN
.
Preliminary
(mean)
(mean)
Sample
mean
SD
FSRQs
0.87
0.03
BL Lacs
0.89
0.02
Total
0.88
0.02
(100%CGB)
(100%CGB)
 In 3 months we have seen mostly flaring blazars like EGRET
 For the two blazar classes no strong differences in 
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Radio to -rays observed correlation
 In recent paper (Kovalev et al. 2009) a correlation between high frequency
radio (15 GHz) and gamma-ray fluxes is showed.
 This set of radio observations are quasi
simultaneous to Fermi gamma-ray fluxes
(Abdo et al 2009, BSL).
 The gamma-ray high variability of
blazars blurs the correlation with the
microwave band.
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Kovalev et al.(2009)
Fraction of WMAP sources detected by Fermi
Preliminary
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009
Conclusions
 Fermi is detecting a significant number (although a small fraction)
of powerful microwave emitters.
 The -wave to X-ray correlation is tight.
 The -wave to -ray correlation is blurred by large gamma-ray
variability of blazars, specially with non-simultaneous data.
PLANCK data along with Fermi ones, being both operated in survey
mode, will give us unprecedented set of real simultaneous data.
E. Cavazzuti - The Extreme Sky 2009 - 13 October 2009