Post on 28-Jun-2020
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Leptonic and hadronic modelingof γ-ray blazars
Matteo Cerruti
CfA-SAO
What are we learning from the γ-ray sky?Oct 12, 2013
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Caveat lector!
I The talk will be focused on emission in the sourceI I neglect any contribution produced in the path from the
source to usI I assume that EBL models are correct (Franceschini et al.)I I assume that the standard model is correct (no axions)
I Modeling the stationary SED, not variability
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Blazars
Blazar : radio-loud AGN, with relativistic jet pointing in thedirection of the Earth
⇒ the emission from the jet dominates over other components
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Blazars
Blazar characteristics :
I high polarization
I extreme variability
Blazar classification according to the strength of disc emission /broad emission lines with respect to the continuum
I detection of emission lines in optical/UV spectrum (FSRQs)
I spectrum dominated by non-thermal continuum (BL Lacs)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Blazars
Spectral Energy Distribution characterized by a double bumpBL Lac object distinguished according to the energy of the firstpeak :
I peak in optical: Low-frequency peaked (LBLs)I peak in UV/X-rays : High-frequency peaked (HBLs)
Fossati et al., 1998Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
What are we learning from the γ-ray sky?
Mrk 421: past and current generation of γ-ray instruments
Maraschi et al., 1999 - Abdo et al., 2012
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Leptonic Models
I Low-energy component of the SEDI Synchrotron emission by electrons/positrons in the jet
I High-energy component of the SEDI Inverse Compton scattering off the synchrotron photons (SSC)I Inverse Compton scattering off external photons (EIC)
SED fitting suggests that SSC works well for HBL,EIC required for LBL/FSRQ
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Leptonic Models
I Low-energy component of the SEDI Synchrotron emission by electrons/positrons in the jet
I High-energy component of the SEDI Inverse Compton scattering off the synchrotron photons (SSC)I Inverse Compton scattering off external photons (EIC)
SED fitting suggests that SSC works well for HBL,EIC required for LBL/FSRQ
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
The SSC model
Simplest model (that fits the data) we have:Synchrotron-self-Compton (SSC) model:
I the emitting region is an over-density in the relativistic jet,moving with Doppler factor δ
I filled with a homogeneous magnetic field B
I and a stationary non-thermal population of leptons (e±)
One-zone SSC : at each moment the emission is dominated by one,single emitting region
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
SSC model free parameters are NINE:I Emitting region
I δ Doppler factorI B magnetic fieldI R size (spherical source)
I Lepton population (broken power-law):I α1 and α2 the two slopesI γmin, γbreak and γMax
I K normalization factor
Reduced to SEVEN if γmin and γMax low and high enough
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
Standard blazar observables are SIX:
I the frequency and luminosity of the Synchrotron peak
I the frequency and luminosity of the Compton peak
I the X-ray and the γ-ray spectral index
The system cannot be closed → additional constraints fromvariability time-scale
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
Analytical approach to constrain the parameters developed byTavecchio et al. (1998):
I define a list of analytical equations linking parameters andobservables
I solve the system for a given set of observables
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
Constraints following the Tavecchio approach (for Mrk 421)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
In the recent years several improvements:
I Finke et al. 2008
I Mankuzhiyil et al. 2011
I Zhang et al. 2012
All of them are χ2 minimization algorithms.
I → error bars on parameters!
In general, with Fermi and IACTs data we can improve theapproach of 15 years ago, and provide significant constraints onthe parameter space.
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
We have developed (Cerruti et al. 2013) a new numericalalgorithm which extends the work by Tavecchio et al.Definition of a new set of SEVEN observables:
I the frequency and luminosity of the Synchrotron peak
I the flux and the slope measured by Fermi
I the flux and the slope measured by IACTs
I the X-ray spectral index
The system is in principle solved, and additional constraints onlynarrow the solution found
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Constraining the SSC model parameters
The algorithm is composed by three steps:
I production of a grid of SSC models, finding the expression ofthe observables
I fit of the grid as a function of the parameters
I solution of the system of equations (spanning theuncertainties on the observables)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Application to 1RXS J101015.9-311909
SSC model, including the uncertainty on the parameters
Cerruti et al. 2013, A&A 558, A47
δ > 30, B=(5-40) mG, R=(5− 100)× 1015 cmMatteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Application to 1ES 0229+200
SSC model, including the uncertainty on the parameters
VERITAS, presented at ICRC’13, submitted to ApJ
δ > 53, B=(0.8-3) mG, R=(5− 30)× 1015 cmMatteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
If the γ-ray emitting region is located in a bright external photonfield (BLR, dust torus, accretion disc,...)→ EIC can dominate over SSC
Problem: increase in the number of free parameters→ Model can be constrained only by adding additional hypothesis(on the energy budget, the location of the emitting region, thevariability time-scale, ecc...)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
If the γ-ray emitting region is located in a bright external photonfield (BLR, dust torus, accretion disc,...)→ EIC can dominate over SSC
Problem: increase in the number of free parameters→ Model can be constrained only by adding additional hypothesis(on the energy budget, the location of the emitting region, thevariability time-scale, ecc...)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
New approach (Dermer et al., 2013, arXiv:1304.6680):Near-equipartition relation + log-parabolic particle distribution
New variables:
I L: luminosity synchrotron component
I νs : synchrotron peak frequency
I τ : variability time-scale
I b: curvature index of the particle distribution
I ζe , ζs , ζ∗: equipartition factors
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
Application to the FSRQ 3C454.3 (GeV blazar, not TeV!)
I External photon field considered: dust torus + combination ofemission lines
I SED well reproduced in two different flux states
I Break in the Fermi/LAT spectrum well reproduced(due to : intrinsic curved particle population, transition toKlein-Nishina regime, superposition of EIC on differenttemperature components)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
Application to 3C454.3
Cerruti et al. 2013, ApJL 771,L4
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
BL Lac objects and SSCFSRQs and EIC
External inverse Compton
Application to 3C454.3:
I The break in the Fermi-LAT spectrum is nicely reproduced
I δ=20-40; B = 0.6− 0.8 G, close to equipartition
I Variability associated to the gamma-ray emitting region, andnot the external photon field
I Emitting region located at the outer edge of the BLR
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
In hadronic models the high-energy bump is ascribed to emissionassociated with protons in the emitting region
I synchrotron emission from protons
I secondary particles coming from p-γ and p-p interactions
Interesting also for the possible links with the extra-galactic cosmicrays and neutrino astronomy
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Modelling Mrk 421 Emission
Example of hadronic modeling of Mrk 421 (with two differentcodes)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Modelling PKS2155-304 Emission
Multi-wavelength observation of PKS2155-304 during a low state(HESS, Fermi, RXTE, Swift and ATOM) (Aharonian et al. 2009)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic Modeling of PKS 2155-304
Parameterδ 30ne [1/cm3] 6.0e+2γe,min 1γe,brk 4e+3γe,max 6e+4Γe,1 2.0Γe,2 4.32η = np/ne 20γp,min 1γp,max 1e+9Γp 2.0B [G] 80R [cm] 5.2e+14
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic Modeling of PKS 2155-304
Parameterue [erg/cm−3] 2.2e-3up [erg/cm−3] 3.7e+2uB [erg/cm−3] 2.5e+2ue/uB 8.5e-6up/uB 1.5Ljet [erg/s] 4.2e+45τvar [hr ] 0.2
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
Can we test hadronic models in the near future?
I Interesting perspectives for CTA: hardening of the TeVspectral slope due to the emission from secondary leptons
I Simulation of CTA observations of PKS 2155-304 assumingboth models: SSC and hadronic
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
Two different models considered, withB=80 G and 50 G
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
Simulations of 200 CTA spectra, and fit with a log-parabola
Zech and Cerruti, 2013, arXiv:1307.3038
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
Can we test hadronic models in the near future?
I Interesting perspectives for CTA: hardening of the TeVspectral slope due to the emission from secondary leptons→ Can be distinguished using 50h of CTA observations(trigger low-flux state?)
I In hard-X-rays: secondary pairs fill the gap between the twobumps much more than SSC modelsSimultaneous MWL campaigns using NuStar and/or Astro-Hsatellites could help us
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Hadronic models
Other models based on hadrons:
I If hadrons can escape the source, they will interact in the pathfrom the blazar to us, producing a cascade component
I ⇒ they can produce as well a hardening of the VHE spectrum
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Introduction
Leptonic ModelsBL Lac objects and SSCFSRQs and EIC
Hadronic models
Conclusions
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
Conclusions
Theoretical modeling of blazar emission:I Leptonic models:
I SSC model working for HBLs, and well constrained forGeV-TeV detected objects
I EIC model required for LBLs / FSRQs
I Hadronic models:I As good as SSC for HBLsI The two models can be disentangled in hard-X-rays and VHE
(with CTA)
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars
IndexIntroduction
Leptonic ModelsHadronic models
Conclusions
THANKS !
Matteo Cerruti Leptonic and hadronic modeling of γ-ray blazars