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 Technology
University of Maryland Baltimore County (UMBC) Solid state, quantum optics, atmosphere, high energy astrophysics. ~30 research astronomers at Goddard
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 ε b 1 TeV λογ ( ν L ν ) M87, almost a blazar relativistic e + Synchrotron photons ⇒ Cooling=escape high energy photons Tavecchio et al 01 Synchrotron-Self Compton λογ ( ν ) (SSC)
PKS 2155-304 2-minute doubling time in TeV energies. (Aharonian et al. 2007)
How can we get such a fast variation? R Γ 1 t var,min = R � = θ � (1 � � cos � ) c � Case A: the emission region occupies the entire jet cross section (Aharonian et al 2007). Then R blazar >R BH, δ >R blazar /ct var >100 • Case B: Localized energy dissipation with R blazar <R BH (e.g. Begelman et al. 2008, Giannios et al. 2009) γ -ray pair production transparency • requirement δ >50
PKS 2155-304: A Cubic variation of the TeV emission relative to the X-rays ( Α haronian et al. 2009)
SSC models predict quadratic variations: • Variations of the injected electron distribution n e : 2 L Synch � n e , L SSC � n e U Synch � n e L Synch � n e • What about electrons upscattering SSC photons? • This is the second order self-Compton scattering, SSC2. 3 L SSC 2 � n e U SSC � n e L SSC � n e Yes, we can have cubic variations!
Speed threshold for SSC2 • In the comoving frame: a significant portion of the SSC photons at energies above the synchrotron cutoff ε synch / δ is in the Thomson regime for electrons of Lorentz factor at least γ ~ ε TeV / δ . CUBIC THRESHOLD: ( � Synch / � )( � TeV / � ) < 1 1/ 2 � (2 � 10 � 2 � 2 � 10 1/ 2 = 200 6 ) � > ( � Synch � TeV ) The higher δ is, the more extended in high energies the green zone is and the more pronounced the SSC2 emission will be.
Numerical results: Cubic variations for a 2155-like spectrum require δ >~300. Detailed data fit pending.
How far from the black hole is the GeV emission of powerful blazars produced? Amanda Dotson 1 Markos Georganopoulos 1,2 Demosthenes Kazanas 2 Eric Perlman 3 1 University of Maryland, Baltimore County 2 NASA/Goddard Space Flight Center 3 Florida Institute of Technology
Two very different schools
The near camp: Few hour GeV variability puts the blazar inside the BLR Tavecchio et al. 2010 For Γ = δ =10 , t var =10 4 s ~ 3 hours), maximum source size r=c t var / δ =3 x 10 15 cm. Assuming a jet opening angle θ =1/ Γ , an upper limit on the distance of the blazar from the central engine is R=r θ = r / Γ = 3 x 10 16 cm. This distance is smaller than the BLR size (few x 10 17 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.
The far camp: Multiwavelenth polarimetric observations put the blazar at ~10 pc from the central engine Agudo et al. 2010
Cooling at the onset of the KN regime
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.
B. Blazar outside the BLR Seed photons for GeV inverse Compton emission: IR dust photons Scattering takes place in the Tho m son 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
Example: Flare inside the BLR PKS 1454-354 Abdo et al. 2009
Example: Flare outside the BLR 3C 273 Abdo et al. 2010
Are jets monoparametric engines? The question and the first steps Eileen Meyer 1 Markos Georganopoulos 2,3 Giovanni Fossati 1 Matt Lister 4 1 Rice University 2 University of Maryland, Baltimore County 3 NASA/Goddard Space Flight Center 4 Purdue University
The blazar sequence
The blazar sequence and blazar envelope What are the sources below the blazar sequence? The sequence is made up by the most aligned objects. The envelope should contain all the un-aligned ones. Meyer et al. 2011
What if the physical properties of a jet depend only on one parameter, the jet kinetic power?
How do you measure jet kinetic power? Cavagnolo et al. 2010
Getting the extended low frequency luminosity Meyer et al. 2011
Getting the extended low frequency luminosity Meyer et al. 2011 As θ increases, beaming increases, core dominates over extended at lower energies
Are the tracks there? Yes, but not as we thought they would be. Meyer et al. 2011 Powerful sources=> Single velocity flows Weak sources=> velocity profiles Wide range in v peak at low powers (<42) Radio galaxies have universally low synch. peaks
Another view of the tracks Strong dependence of L peak on R at all powers = The envelope is a result of beaming
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
Fermi?
The Envelope is there. Another forbidden zone?
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