Leptonic and hadronic modeling of -ray blazars · 2016-05-18 · Mrk 421: past and current...

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


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


IndexIntroduction


Conclusions

Introduction

Leptonic ModelsBL Lac objects and SSCFSRQs and EIC

Hadronic models

Conclusions


IndexIntroduction


Conclusions

Blazars

Blazar : radio-loud AGN, with relativistic jet pointing in thedirection of the Earth

⇒ the emission from the jet dominates over other components


IndexIntroduction


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)


IndexIntroduction


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


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


IndexIntroduction


Conclusions

BL Lac objects and SSCFSRQs and EIC

Introduction


Hadronic models

Conclusions


IndexIntroduction


Conclusions


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


IndexIntroduction


Conclusions


Introduction


Hadronic models

Conclusions


IndexIntroduction


Conclusions


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


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Conclusions


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


IndexIntroduction


Conclusions



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


IndexIntroduction


Conclusions



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


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Conclusions



Constraints following the Tavecchio approach (for Mrk 421)


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Conclusions



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.


IndexIntroduction


Conclusions



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


IndexIntroduction


Conclusions



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)


IndexIntroduction


Conclusions


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


Conclusions


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


Conclusions


Introduction


Hadronic models

Conclusions


IndexIntroduction


Conclusions


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...)


IndexIntroduction


Conclusions



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


IndexIntroduction


Conclusions



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)


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Conclusions



Application to 3C454.3

Cerruti et al. 2013, ApJL 771,L4


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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


IndexIntroduction


Conclusions

Introduction


Hadronic models

Conclusions


IndexIntroduction


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


IndexIntroduction


Conclusions

Modelling Mrk 421 Emission

Example of hadronic modeling of Mrk 421 (with two differentcodes)


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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)


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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


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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


IndexIntroduction


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


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Conclusions

Hadronic models

Two different models considered, withB=80 G and 50 G


IndexIntroduction


Conclusions

Hadronic models

Simulations of 200 CTA spectra, and fit with a log-parabola

Zech and Cerruti, 2013, arXiv:1307.3038


IndexIntroduction


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


IndexIntroduction


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


IndexIntroduction


Conclusions

Introduction


Hadronic models

Conclusions


IndexIntroduction


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)


IndexIntroduction


Conclusions

THANKS !


Leptonic and hadronic modeling of -ray blazars · 2016-05-18 · Mrk 421: past and current...

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Transcript of Leptonic and hadronic modeling of -ray blazars · 2016-05-18 · Mrk 421: past and current...