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Blazars: Can they (sometimes) be much faster than we thought? Markos - - PowerPoint PPT Presentation
Blazars: Can they (sometimes) be much faster than we thought? Markos - - PowerPoint PPT Presentation
Blazars: Can they (sometimes) be much faster than we thought? Markos Georganopoulos 1,2 Demosthenes Kazanas 2 Eric Perlman 3 Adam Higuera 1 1 University of Maryland, Baltimore County 2 NASA/Goddard Space Flight Center 3 Florida Institute of
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εb λογ (νLν ) λογ (ν)
Cooling=escape
Tavecchio et al 01
1 TeV
What are the extragalactic TeV sources?
The ~sub-pc scale relativistic jets of blazars, active galaxies with TeV emitting jets pointing to us. Low power-FR I radio galaxies are the parent population
relativistic e + Synchrotron photons ⇒ high energy photons Synchrotron-Self Compton (SSC)
M87, almost a blazar
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PKS 2155-304 2-minute doubling time in TeV energies. (Aharonian et al. 2007)
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How can we get such a fast variation?
θ
= 1 (1 cos)
R
Γ
tvar,min = R c
Case A: the emission region occupies the entire jet cross section (Aharonian et al 2007). Then Rblazar>RBH, δ>Rblazar/ctvar>100
- Case B: Localized energy dissipation with
Rblazar<RBH (e.g. Begelman et al. 2008, Giannios et al. 2009)
- γ-ray pair production transparency
requirement δ>50
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PKS 2155-304: A Cubic variation of the TeV emission relative to the X-rays (Αharonian et al. 2009)
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SSC models predict quadratic variations:
- Variations of the injected electron distribution ne:
LSynch ne, LSSC neUSynch neLSynch ne
2
- What about electrons upscattering SSC photons?
- This is the second order self-Compton scattering, SSC2.
LSSC 2 neUSSC neLSSC ne
3
Yes, we can have cubic variations!
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Speed threshold for SSC2
- In the comoving frame:
a significant portion of the SSC photons at energies above the synchrotron cutoff εsynch/δ is in the Thomson regime for electrons of Lorentz factor at least γ~εTeV/δ.
CUBIC THRESHOLD:
> (SynchTeV )
1/ 2 (210 2 210 6) 1/ 2 = 200
(Synch /)(TeV /) <1
The higher δ is, the more extended in high energies the green zone is and the more pronounced the SSC2 emission will be.
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Numerical results: Cubic variations for a 2155-like spectrum require δ>~300. Detailed data fit pending.
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Amanda Dotson1 Markos Georganopoulos1,2 Demosthenes Kazanas2 Eric Perlman3
1University of Maryland, Baltimore County 2NASA/Goddard Space Flight Center 3Florida Institute of Technology
How far from the black hole is the GeV emission of powerful blazars produced?
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Two very different schools
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The near camp: Few hour GeV variability puts the blazar inside the BLR
This distance is smaller than the BLR size (few x 1017 cm, Kaspi et al. 2007) => the GeV emission must be produced inside the BLR. If small parts of the jet can produce the GeV emission (e.g Begelman et al 2008, Giannios et al 2009), short variations can take place further out. For Γ=δ=10, tvar=104 s ~ 3 hours), maximum source size r=c tvar/δ=3 x 1015 cm. Assuming a jet opening angle θ=1/Γ, an upper limit on the distance of the blazar from the central engine is R=rθ=r /Γ= 3 x 1016 cm.
Tavecchio et al. 2010
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The far camp: Multiwavelenth polarimetric observations put the blazar at ~10 pc from the central engine
Agudo et al. 2010
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Cooling at the onset of the KN regime
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- A. Blazar inside the BLR
Seed photons for GeV inverse Compton emission: UV BLR photons Scattering takes place at the onset of the Klein-Nishina regime => electron cooling time becomes ~ energy independent variations of high-energy emission ~ almost achromatic => energy-independent flare decay time Steady photon index during the flare.
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- B. Blazar outside the BLR
Seed photons for GeV inverse Compton emission: IR dust photons Scattering takes place in the Thomson regime => electron cooling time is ~ energy dependent ~ 1/γ variations of high-energy emission ~ energy dependent => energy-dependent flare decay time Steady photon index during the flare
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Example: Flare inside the BLR
PKS 1454-354 Abdo et al. 2009
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Example: Flare outside the BLR
3C 273 Abdo et al. 2010
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Eileen Meyer1 Markos Georganopoulos2,3 Giovanni Fossati1 Matt Lister4
1Rice University 2University of Maryland, Baltimore County 3NASA/Goddard Space Flight Center 4Purdue University
Are jets monoparametric engines? The question and the first steps
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The blazar sequence
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The blazar sequence and blazar envelope
What are the sources below the blazar sequence?
Meyer et al. 2011
The sequence is made up by the most aligned objects. The envelope should contain all the un-aligned ones.
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What if the physical properties of a jet depend
- nly on one parameter, the jet kinetic power?
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How do you measure jet kinetic power?
Cavagnolo et al. 2010
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Getting the extended low frequency luminosity
Meyer et al. 2011
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Getting the extended low frequency luminosity
As θ increases, beaming increases, core dominates
- ver extended at lower energies
Meyer et al. 2011
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Powerful sources=> Single velocity flows Weak sources=> velocity profiles Wide range in vpeak at low powers (<42) Radio galaxies have universally low synch. peaks
Are the tracks there? Yes, but not as we thought they would be.
Meyer et al. 2011
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Another view of the tracks Strong dependence of Lpeak on R at all powers = The envelope is a result of beaming
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Low power sources: two populations?
Here the sequence appears broken Alternative: Simple jets (FR II) vs. Decel. jets (FR I) “FR II” BL Lacs have low peaks, high core dominance
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Fermi?
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The Envelope is there.
Another forbidden zone?