1. Gamma-ray emission along the radio jet:
studies with Planck, Metsähovi and Fermi
Esko Valtaoja
Tuorla Observatory, University of Turku, Finland
Metsähovi Radio Observatory, Aalto University +
Tuorla-Metsähovi AGN Team: Merja Tornikoski, Anne
Lähteenmäki, Jonathan Léon-Tavares, Elina Nieppola,
Joni Tammi, Talvikki Hovatta*, Venkatessh Ramakrishnan
*presently at California Institute of Technology

2. [courtesy Alan Marscher] CLOSE to BH/accretion disk (inside BLR):
gamma-rays precede radio
variations (VLBI zero
epoch, beginning of a
millimeter flare)‏
little or no correlation with
radio variations
DISTANT, at or downstream of the radio core (outside the BLR):
- gamma-rays simultaneous, or after,
the beginning of radio variations
- correlation with radio variations

3. DISTANT! EGRET: Valtaoja and Teräsranta 1995, 1996
(EGRET Phase 1 all-sky survey, Metsähovi radio sample)‏
DISTANT!
BLACK: EGRET detections
HIGHLY POLARIZED QUASARS
ARE STRONGEST GAMMA-RAY
EMITTERS
STRONGEST GAMMA-RAYS DURING
RISING OR PEAKING MM-FLARES
 FROM SHOCKS

4.
[Ramakrishnan et al.
in preparation] 4

5. EGRET: Lähteenmäki and Valtaoja 2003
(final EGRET data set, Metsähovi sample)‏
Quasars BL Lacs
filled: detections
open: nondetections
(upper limits)‏
STRONGEST GAMMA-RAY EMISSION DURING RADIO
FLARE RISE/PEAK  SHOCKS
- BL LACS MUCH WEAKER GAMMA-RAY EMITTERS
- STRONG/WEAK EMISSION (HPQ/BLLAC?) TWO DIFFERENT MECHANISMS?
average: gamma 2 months after the beginning of the radio flare = Jorstad et al. (VLBI) 2001

6. 3C 279 Lindfors et al. (2005, 2006)‏ The longer the inter-
val from the onset of
the radio flare to the
gamma-ray flare
(=the distance from
the radio core to the
site of  emission
downstream),
the weaker the gamma

7. 2008- Fermi: wealth of -ray data, monitoring
case for “distant”  origin is much stronger
no direct observational evidence for “close” origin
observations point towards “distant” origin:
radio-gamma correlations, delays from radio to 
case for several “distant”  sites is strong
gamma-rays from upstream, at, and downstream
of the radio core as a disturbance propagates
along the jet

8. OJ 287: 14 pc downstream
the RC (Agudo et al. 2011)‏
BL Lac: slightly
upstream of the
radio core
(Marscher
et al. 2008)‏
: similar
case (Marscher
et al. 2010)‏
around the RC:
- in 2/3 of 34 -AGN
(Marscher et al. 2012)‏
- 3C345 (Jorstad et al.
2012)‏
- 3C454.3 (Jorstad et al.
2010)‏
- AO (Agudo
et al. 2011)‏
- 3C279 (Abdo et al. 2010)‏
- etc...
3C 345: up to 40 pc down-
stream (Schinzel et al. 2010)‏

9. RADIO/GAMMA
CORRELATIONS:
1) delays from cm to mm
 use mm-data!
2) look at beginnings, not
peaks in searching
the temporal order!
[Raiteri et al 2012]

10. Léon-Tavares et al. (2011): monthly  vs. Metsähovi
37 GHz radio data (full Fermi data analysis is in preparation)‏
(full Fermi data in preparation)‏

11. Léon-Tavares et al. 2011: average delay from the onset of a
mm-flare to -flare peak  70 days (= Lähteenmäki & Valtaoja
2003; Jorstad 2001)‏

12. QUASARS: CORRELATION FOR MONTHLY AVERAGES (Léon-Tavares et al. 2011)‏
The strongest  flares from HPQ, BL Lacs weaker, no r/ correlation?

13. IS THERE ROOM
for the required
mid/near-IR peaking
synchrotron component
(purely theoretical!)‏
in ”close to BH” scenarios?
[state-of-art EGRET for
3C 279, Hartman et al. 2001]
[a random recent theoretical
model, Joshi et al. 2012]

14. Planck
Collaboration:
4-epoch simultaneous
radio-to-gamma
SEDS of 100
radio-brightest
Northern AGN
(work in progress)‏

15. NO ROOM (?)‏
Planck data,
Aatrokoski et
al. 2011
quite flat spectra (shocks) up
to 1012 Hz, joining smoothly
the optical with 0.5 break:
no room for more IR spectral
components
gamma must come from the shocks, in particular from the most recent one

16. Some open questions / challenges:
the ”radio core”: 2 months delay from what?
seed photons: SSC, Mach disk, dust torus, ”dragged” BLR, ...?
quasars and BL Lacs / different  mechanisms, sites?
rapid variability – turbulent multizone models (Marscher)‏
signatures of absorption (e.g. Poutanen, tomorrow morning)?
some jets starting close to the black hole (M87)? WE
- wait (and wait, and wait...) for the final Planck data to model the
4- epoch radio to gamma SEDs with unprecedented accuracy
- cross-correlate all Fermi data with Metsähovi + other radio
- develop new, realistic (spectra based on data...) multicomponent
models which reproduce MF variations, SEDs and VLBI data
- nonvirial (”jet dragged” BLRs?

17. OUTFLOWING
NONVIRIAL BLR
[courtesy Jonathan
Léon-Tavares]