F-GAMMA: multi-frequency radio monitoring of Fermi blazars E. - - PowerPoint PPT Presentation

F-GAMMA: multi-frequency radio monitoring of Fermi blazars

• E. Angelakis, I. Myserlis, & J. A. Zensus

Max-Planck-Institut für Radioastronomie, Auf dem Huegel 69, Bonn 53121, Germany

• n behalf of the F-GAMMA team

➡ almost 90 mostly Fermi sources ➡ 2.64 - 142, 229, 345 GHz at 12 frequency steps ➡ mean cadence 1.3 months

the F-GAMMA program (Jan 2007 — Jan 2015):

➡ localise the gamma-ray emission site ➡ understand the broad-band variability ➡ estimate the properties of the emitting elements

Fuhrmann, Angelakis et al., 2016, A&A, 596, A45

gamma-ray emission site

gamma rays production site?

Karamanavis et al A&A 590, A48 (2016) Fuhrmann et al MNRAS 441, 1899 (2014)

Dust torus Accretion disk ~ 1 – 10 pc Broad Line Region (BLR) <~ 1 pc γ-ray emission region γ rays Relativistic jet Dust torus Accretion disk ~ 1 – 10 pc Broad Line Region (BLR) <~ 1 pc γ-ray emission region Relativistic jet

Fuhrmann et al MNRAS 441, 1899

the exercise:

➡ ~ 3.5-year light curves of 54 Fermi

blazars

➡ search for radio/γ-ray correlations

relative timing of flares results:

➡ 9 cases significant ➡ radio bands delay with respect to

gamma rays interpretation:

➡ Delay origin: opacity synchrotron

self-absorption (SSA) dominated:

• γ rays escape immediately while

radio progressively later

no significant correlation significant correlation

ν1 ν2 ν3 ν4

“tau=1” surface for ν4>ν3>ν2>ν1 gamma-ray emission site jet base BH

rBH,base rbase,γ rbase,ν

need to solve: hence rbase,γ is a lower limit for the distance rBH,γ rBH,γ = rBH,base + rbase,γ

rr,γ

for PKS1502+106 Karamanavis et al A&A 590, A48, 2016

rBH,γ ≥ 1.9 ± 1.1 pc

with Abdo et al. 2010

RBLR ≈ 0.1 pc

for 3C454.3 Fuhrmann et al MNRAS 441, 1899, 2014

rBH,γ ≥ 0.8 − −1.6 pc

with Bonnoli et al. 2011

RBLR ≈ 0.2 pc

rbase,ν :

• 1. use VLBI-only core-shifts

(tedious, hard task etc)

• 2. radio-only time-lags with

proper motion from VLBI

50 100 150 200 250 300 350 frequency [GHz] 20 40 60 80 100 time lag [days] = +

1

∆rrγ =

cβappτ source

rγ

sinθ

from gamma-radio relative timing (DCCF)

physical processes at the emission elements

the Radiopol since 2015 …

➡ almost 18 Fermi sources ➡ 2.64 - 43 GHz ➡ LP at 2.64, 4.85, 8.35, 10.45 and 14.6 GHz ➡ CP at 2.64, 4.85, 8.35, 10.45, 14.6, 23.05 GHz ➡ mean cadence 2 weeks

Myserlis, Angelakis et al. 2016Galax…4…58M Angelakis, Myserlis & Zensus, Galaxies, doi: 10.20944/preprints201708.0108.v1

the Radiopol since 2015 …

➡ almost 18 Fermi sources ➡ 2.64 - 43 GHz ➡ LP at 2.64, 4.85, 8.35, 10.45 and 14.6 GHz ➡ CP at 2.64, 4.85, 8.35, 10.45, 14.6, 23.05 GHz ➡ mean cadence 2 weeks

Myserlis, Angelakis et al. 2016Galax…4…58M Angelakis, Myserlis & Zensus, Galaxies, doi: 10.20944/preprints201708.0108.v1

the Radiopol since 2015 …

➡ Uncertainties:

• LP degree: 0.1 %
• CP degree: 0.1—0.2 %
• EVPA: 1°

➡ near future: 90 srcs, 5 LP and 6 CP over at least 8 + 2 +…

years

Myserlis, Angelakis et al. 2016Galax…4...58M Myserlis et al. 2017, A&A, arXiv: 170604200M

the picture: variability caused by episodic activity that undergo spectral evolution. We assume:

➡ magnetised jet with partially uniform magnetic field, ➡ occasional traveling disturbances, ➡ particles at the shocked areas radiate flaring emission

which undergoes spectral evolution 3C279 3C454.3

Angelakis, Myserlis & Zensus, 2017Galax…5...81A Myserlis et al. in prep.

2006.7 2014.9 2006.7 2014.9

B

jet shape

Line of sight

Cell Slab

ν

Myserlis, Angelakis et al. 2016Galax...4...58M, based on Hughes et al. (1989)

B= B0 (r/r0)-q n(γ)d(γ) = n0 γ -s dγ, γ>γi

ν

Line of sight

n0

0 = n0k s+3

6

E0

min = Emink 1

3

B0 ∼ kB

Density Lower energy cutoff B-field strength

k compression factor

Cell jet shape

the high-γmin regime:

➡ each cell has a 100% uniform B-field parallel to the jet with

5% of the amplitude of the local field

➡ B0 ~ 5 mG

Shock parameters:

➡ Compression factor: k = 0.8 (mild shock) ➡ γmin~10 4 ➡ Doppler factor: D ~ 30


Consistent with Dvar at 37 GHz
 Hovatta et al. (2009) Jet plasma parameters (un-shocked jet)

➡ Density: n0 = 10 - 100 cm

• 3

➡ Magnetic field coherence length: 9 pc

Angelakis, Myserlis & Zensus, 2017Galax...5...81A Myserlis et al., Galaxies, vol. 4, issue 4, p. 58 Myserlis, Angelakis et al.,in prep.

Observed lightcurves

8.35 GHz

Synthetic lightcurves

8.35 GHz I (Jy) LP (%) χ (°) CP (%) MJD

Myserlis, Angelakis et al.,in prep. Myserlis et al., Galaxies, vol. 4, issue 4, p. 58

line of sight

17

the low-γmin regime: NGC 4845

Irwin et al, 2015,ApJ…809..172I

➡ evolving convex radio spectrum with a peak around 3-5 GHz ➡ LP: practically zero (0.1–0.5 %) at both 1.5and 5 GHz ✘ ➡ CP:

• unusually high at 1.5 GHz: 2–3 % ✔
• zero at 5 GHz ✔

we examined whether the high CP is caused by converting linear to circular polarisation 
 Realisation

➡ conical adiabatically expanding outflow ➡ random B-field ➡ γmin ∼10–100 


We find:

➡ there is transformation of LP to CP at 1.5 GHz Faraday

conversion, hence:

• the low LP and high CP degrees 


➡ Low LP at 5 GHz cannot be reproduced with


this realisation.

• an excess of low-energy magnetised plasma within or

around the flow may be causing de-polarisation through Faraday rotation.


To summarise:

➡ vast dataset: 281 observing sessions , more than 40 proposals , more than 40

papers

• cross correlation with gamma rays: location of the gamma-ray emission
• internal shocks as the variability mechanism
• mildly relativistic/powerful radio jet in Narrow Lines Seyfert 1 galaxies similar to

bazars

• Scale Invariant Jets: From Blazars to Microquasars
• … etc

To summarise:

➡ polarisation: 90 srcs, 5 LP and 6 CP over at least 8 + 2 +… years

• 11300 data points with Full-Stokes (I, Q, U, V)

➡ Toy model: shock-driven variability and evolution works well both at:

• high γmin regime
• low γmin regime
• and the reproduction of physical processes

Thank you!

Emmanouil Angelakis, Ioannis Myserlis & J. Anton Zensus

Max-Planck-Institut für Radioastronomie, Auf dem Huegel 69, Bonn 53121, Germany