Where and how gamma-rays are produced in AGN jets

TAUP, 10 Sept. 2015

Scientific contributors :

Thomas P. Krichbaum, Jeff A. Hodgson, Lars Fuhrmann, E. Angelakis, J. Anton Zensus [MPIfR, Bonn]

Alan P. Marscher, Svetlana G. Jorstad [Boston University, USA]

Benoit Lott [CNRS Bordeaux, France]

Markus Böttcher [Ohio University, USA]

Mark A. Gurwell [Harvard-Smithsonian Center for Astrophysics, USA]

David J. Thompson [NASA, GFSC, USA]

Bindu Rani [brani@mpifr-bonn.mpg.de]Postdoctoral Research FellowMax Planck Institute for Radio Astronomy, Bonn, Germany

On behalf of the Fermi-LAT Collaboration

Outline

Introduction

What do we know

Recent results of our study

Summary and near future outlook

Introduction Blazars

Urry & Padovani (1996)

Relativistic jet outflow with Г – up to 50 θ – 1/Г

Fermi/LAT

Image credit: NASA/GSFC

Gamma-ray sky seen by Fermi/LAT

The Fermi era

High-energy radiation seems to be related to relativistic particles accelerated in jets.

>3000 gamma-ray objects ~60% AGN (98% blazars)

Since its launch in 2008, the Fermi-LAT (Large Area Telescope) has revolutionized our knowledge of gamma-ray sky with a combination of high sensitivity, wide field-of-view, and large energy range (about 20 MeV to more than 300 GeV).

Particles accelerated in relativistic jets

Observed gamma-ray -- radio correlations (Agudo et al. 2010, 2011, Jorstad et al. 2010, 2013, Marscher et al. 2008,2010, Fuhrmann et al. 2014, Rani et al. 2013,2014, Max-Moerbeck et al. 2014, Schinzel et al. 2012)

Coincidence of gamma-ray flares often with appearance of new jet components

S5 0716+714

Marscher et al. 2011

Gamma-ray lead radio(Rani et al. 2013)

Where

Within the broad-line region On sub-parsec scales (100-1000 Rs)-- Observed gamma-ray -- radio correlations

(Marscher et al. 2008,2010, Rani et al. 2013, Fuhrmann et al. 2014)

-- Observed gamma-ray spectral break at few GeVs (Abdo et al. 2009, Finke & Dermer 2010, Rani et al. 2013a,b, Tanaka et al. 2011)

Outside the Broad-line Region Down stream the core Coincidence of gamma-ray flares with

-- Appearance of new jet components (Jorstad et al. 2010, 2013, Marscher et al. 2011)

-- Passage of moving components through stationary features in jets (Hodgson et al. 2014, Schinzel et al. 2012, Marscher et al. 2013)

How : Leptonic Models

Synchrotron

Inverse-Compton

Seed photons Synchrotron Self-Compton : synchrotron photons from the jet

External Compton : thermal photons from accretion disk, broad-line region, and/or molecular torus

Broadband Spectral Energy Distribution (SED)

SSC and/or EC ?Böttcher at al. 2002, 2012

How : Hadronic Models

synchrotron

Broadband Spectral Energy Distribution (SED)

p → n+ ; + → +

→ e+e

→ secondary -, e-synchrotron

Proton-induced cascades

Significant fraction of jet power converted into acceleration of protons in strongly magnetized (B ~ several tens of Gauss) environments reaching the threshold for pγ-pion production (Ep ≥ 1019 eV).

Böttcher at al. 2002, 2012

Most recent and exciting results of our study

Using high-resolution VLBI to probe high-energy emission regions

S5 0716+714

Mass : ~109 Mʘ

Redshift : z ~ 0.3 (Nilsson et al. 2008)

Jet Kinematics : θ<5o, β = 43±3 (Lister 2013) Luminosity distance : ~1.5 Gpc (~5.109 light years)

Blazar with a featureless optical spectrum

A very bright GeV-TeV blazar

S5 0716+714 : arcsec to micro-arcsec scales

0.3 parsec

0.9 parsec

86 GHz

Data used August 2008 to September 2013

Gamma-rays : 100 MeV to 300 GeV

VLBI : 7 & 3 mm (VLBA + GMVA)

Fermi

Parsec-scale jet orientation

Determination of inner jet orientation 1. Model fits

2. Flux density-weighted PA average of all the clean delta components

Rani et al. 2014

Position angle and Core flux variations

Gamma-ray flux vs. core flux variations

Gamma-ray flux vs. core flux variations

Gamma-ray flux variations lead 43 GHz core flux variations by 82±39 days

High-energy emission is produced upstream of the core

Gamma-ray flux vs. position angle variations

A significant correlation between gamma-ray flux and PA variations at >99.97% confidence level

Rani et al. 2014

Core flux vs. PA variations

Tentative models

Jet orientation variations :

-- Geometric precession due to a binary black hole -- Precession of jet nozzle

-- Instabilities : KH instabilities and/ or Magnetohydrodynamic instabilities

Thanks for your attentionThanks for your attention