1. On behalf of the Radio-Agile AGN WG
Blazar radio properties and monitoring
Tiziana Venturi
On behalf of the Radio-Agile AGN WG
7th Agile Workshop & The Bright Gamma-ray sky Rome

2. Outline of the presentation
Radio and γ-ray loud AGN
The radio jets and observable quantities
Multiband campaigns and radio/γ-ray studies before the advent of AGILE and FERMI
Current monitoring programs
Radio-AGILE AGN WG – 3C454.3
Overview of future radio facilites

3. Universal Blazar SED Steep FSRQ
Log Luminosity νLν(erg/s)
radio mm
Flat BL Lacs
Adapted from Fossati 2009
A correlation is expected between the variability at low and high energy: γ-ray flare -> radio flare
The few multiband campaigns carried out so far from the mid-90’s are not conclusive

4. Radio power vs γ ray luminosity
FSRQ
BL Lacs
Adapted from Fossati 2009

5. Courtesy of A. Marscher
From the radio point of view, γ-ray loud AGN are Flat Spectrum Radio Quasars and BL Lac objects, i.e. radio sources whose radio emission is aligned at a small angle to the observer’s line of sight.
The “radio core” is actually the base of the jet, and its location depends on the observing frequency. Parsec-scale radio imaging allows a direct look into the inner jets of blazars.

6. 3C279 VLBA 43GHz
The favourable viewing angle and the high intrinsic speed of the radio emitting plasma, lead to strong flux density and structural variability, and superluminal proper motion

7. Distribution of superluminal proper motion in quasars and BL Lacs from VLBA 43 and/or 22 GHz multiepoch maging
Jorstad et al. 2001

9. From the radio point of view, the underlying idea is that a γ-ray flare may be related to a radio flare, and that new superluminal components may be ejected during the radio flare
Multiband observations of γ-ray loud blazars and multiepoch radio imaging are necessary to test this

10. Before the advent of AGILE & FERMI
1) Only a handful of simultaneous multiband campaign carried out on the best known blazars (i.e. 3C279, Mrk 421 …) with a variety of results (Hartmann et al. 2001; Blazejowski et al. 2005).

11. 2) A-posteriori search for correlation between radio and γ-ray flares and superluminal ejections (UMRAO monitoring and EGRET sources, Jorstad et al. 2001)
γ-ray
radio
γ-ray flare
Superluminal ejection

12. Current radio programs - I. Imaging Monitoring
Radio/γ-ray studies of AGN in the AGILE and FERMI era
Current radio programs - I. Imaging Monitoring
MOJAVE
Imaging + monitoring survey (~200 sources) – GHz
TANAMI
southern monitoring of blazars (~80 sources) – 8.4 & 22 GHz
BU Blazar Group
22 & 43 GHz VLBA imaging monitoring of ~ 20 sources
VIPS
VLBI Imaging and Polarimetry Survey, GHz, ~1200 sources
USNO-RRFID
Database of geodetic observations at 2.3/8.4 GHz and 22 GHz
DXRBS
EVN observations at 5 GHz of ~ 100 sources from the DXRBS sample

13. Current radio programs - II. Single dish monitoring
UMRAO
UMich Radio Observatory, full polarization long term monitoring at 4.8, 8.4, 15 GHz of ~ 50 bright sources
Ratan
monitoring survey of ~ 700 bright sources
Metsahovi
long term monitoring (~ & 37 GHz
OVRO
daily monitoring of ~ GHz
FGamma
Eb (11cm to mm)/IRAM (1,2,3 mm) simultaneous monitoring
Medicina and Noto
Monthly monitoring of ~ 30 sources at 5, 8.4 and 22 GHz

14. Radio-AGILE AGN Working Group
Multiepoch parsec-scale imaging of AGILE bursting AGNs
Instruments VLBA
Frequencies GHz and 43 GHz
Number of epochs
On trigger proposal
Active until the end of 2009
Goals
Accurate morphological classification
Evolution of polarimetric properties close to the γ-ray flare
Morphological changes

15. Strategy
First 4 epochs
as soon as the gamma ray burst is announced and separated by one week each
this observation would provide the “zero image” and the evolution
of the polarisation properties close to the flare
Subsequent 6 epochs
once/month
The time spacing of the epochs allows us to sample a
broad range of apparent proper motions, hence of beaming
Comment: source list had to be revised since the first proposal submission, as the brightest γ ray loud blazars are all in the BU Monitoring Program (Marscher)

16. The sample

17. AGILE campaign in the period May 2008 – January 2009 + RXTE (3-20 keV)
The case of 3C454.3
Vercellone et al. 2009
AGILE campaign in the period May 2008 – January 2009 +
RXTE (3-20 keV)
Swift
GASP/WEBT
UMRAO + MOJAVE radio data

18. 3C454.3 in the radio band
z = strong quasar with superluminal motion
7.70 pc/mas along the one-sided jet
Dl Mpc
43 VLBA
βapp (B6) ~ 13.3 – 18.8c
Jorstad et al. 2005

19. Multifrequency light curves
The radio flux density is steadily increasing, and not in the form of flares. The radio peak is reached at a time when the γ-ray emission is not flaring

20. Images from the MOJAVE monitoring in 2007 - 2008
15 GHz - 7 Aug 2007
Total flux density increase due to the radio core (component C)
Flux density of the main jet components stable or decreasing
No proper motion along the jet
No birth of new components so far
From the core variability at 43 GHz it was derived that the source is viewed at θ~1.5° and that Γ~20

21. Main current and future VLBI facilities
In order to look into the inner jets, parsec-scale imaging (mas & sub-mas resolution) is needed
Very Long Baseline interferometry & high radio frequencies (i.e. above 5 – 8.4 GHz)
Main current and future VLBI facilities
Ground
VLBA (δ≥ -30o) : up to 43 GHz, 512 Mbps
GMVA (δ≥ -30o ): up to 86 GHz
LBA (southern hemisphere): up to 22 GHz
European VLBI Network (δ ≥ -10o): up to 22 GHz, 1 Gbps
e-EVN, more flexible and more frequent than EVN

22. Space VLBI in the near future
ASTRO-G –
Dual Pol. – 8.4, 22, 43 GHz
Space Radio Telescope – 2010
327 MHz, 1.6, 4.8, GHz
sub-mas to μas resolutions from 327 MHz to 43 GHz