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Nijil Mankuzhiyil (INFN, Udine U.) Massimo Persic (INAF+INFN, Trieste) Fabrizio Tavecchio (INAF, Milano). Blazars as beamlights to probe the EBL. Problem: EBL, emitted SED: both unknown ! Aim: measure n EBL ( z ) at different redshifts - PowerPoint PPT Presentation
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Blazars as beamlights to probe the EBL
Problem: EBL, emitted SED: both unknown !
Aim: measure nEBL(z) at different redshifts local normalization, cosmic evolution
Tools: homogeneous set @ different redshifts one same model (parameters) at all z
blazars (e.g., High-Peaked BLs [HBLs] )
Emission physics: simple one-zone SSC emission
synchrotron + compton, PL electron spectrum
Nijil Mankuzhiyil (INFN, Udine U.) Massimo Persic (INAF+INFN, Trieste) Fabrizio Tavecchio (INAF, Milano)
One-zone SSC: model parameters:Plasma blob: R, B, j
Electron pop: n0, 1, 2, Ebr, Emin, Emax
Kino+ 2002
Tavecchio + 2001ApJ, 554, 725
Simultaneous multi- obs’s: opticalX-rays HE-ray VHE -ray
Model SED: use SED w/out (EBL-affected) VHE -ray data: 2-minimization SSC model(check structure of multi-D parameter space)
TT
TTTTTT
simulated data
The method (1)
Extrapolate model SED into VHE regime “intrinsic” blazar VHE emission
Observed vs “intrinsic” emission (E,z)
Assume (concordance) cosmology nEBL(,zj) (parametric: anj n)
s i m u l a t e d d a t a
simulated data
simulated data
…the method (2)
EBL de-absorbed
Aharonian+ 2009ApJ, 696, L150
HESS
FERMI
RXTE
ATOM
… assumed electron spectrum is triple-PL …
… caveat…
Swift
Checking the method … locallyPKS 2155-304z = 0.12
SSC param’smin= 1br1 = 1.4104
br2 = 2.3105
max= 3106
1 = 1.32 = 3.23 = 4.3
B = 0.018 GR = 1.51017
cm= 32
data: Aharonian+ 2009 ApJ, 696, L150
… our effort
H.E.S.S.
Fermi
ATOM Swift, RXTE
R t 12 hr OK
observed
SSC parametersfrom 2 minim.
ne=150 cm
min= 1br = 2.9104
max= 8105
1 = 1.82 = 3.8
B = 0.056 GR = 3.871016 cm= 29.2
p
r
e
l
i
m
i
n
a
r
y
Stecker 1999
z=0.12
p r e l
i m i
n a r y
Stecker & de Jager 1998
Malkan & Stecker 1998
Franceschini + 2008
z=0.1
z=0.003
z=0.01z=0.03
z=0.3
z=0.12
p r
e l
i m
i
n a
r
y
(E,)max by (for head-on collision)
2.5 E, TeV
m
Heitler 1960
(E,z) = dl/dz x/2 nEBL() (2xE/(1+z)2) ddx dz
(E,,) [1 – 2(mec2)2 / E (1-cos)]1/2
0 z zs
> 2(mec2)2 / [Ex(1+z)2]
For EBL photon energies > 2(mec2)2 / E (1-cos)
x 1-cos
nEBL(,z) unknown parameterize nEBL(nzj) = an,j n
(E,,)
Stecker 1971
cosmology
Stecker 1999
Optical depth
Conclusion
Cons: indirect measurement of EBL method depends on blazar model
Pros: unbiased method no assumptions on EBL, blazar SED SSC well tested locally on different emission states
Need: simultaneous multi- obs’s of several blazars in shells of z possibly each source seen @ different levels of activity (to increase statistics)
plan simultaneous obs’s involving IACTs + Fermi + X-rays + optical
Aim: to probe EBL out to z 1 with Fermi/LAT + current/upcoming enhanced IACTs ( + x-ray, optical tel’s )
( long live Fermi to see CTA / AGIS !! )
Check: on local (z=0.12) blazar PKS 2155-304 deduced ’s within reasonable range
Thanks