Speaker: Dr. Emmanouil Angelakis, MPI for Radio Astronomy, Bonn

Title: "Understanding the AGN physics with multi-band monitoring of Fermi-GST blazars"

Abstract:
From the few percent (< 10 %) of galaxies that harbor hyperactive nuclear
regions - in terms of the fraction of emission produced there relative
to the total energy output (Active Galaxies), blazars comprise the most
episodic manifestation of activity triggered and sustained by the
presence of a supermassive black hole accreting environmental material.
Though relatively rare a class of active galaxies (AGNs), blazars (FSRQs
and BL Lacs) provide a unique probe to extreme physics otherwise
inaccessible. The basic ingredient of the theoretical framework for the
explanation of the blazar phenomenon is a relativistic plasma flow
closely aligned to the observer’s line-of-sight, which reveals itself
through complex effects induced by the relativistic character of the
flow. The emitted radiation, spaning practically over the entire
spectrum, traces a characteristic "double-humped" spectral energy
distribution; its low energy peak being attributed to incoherent
synchrotron processes, while the high energy one to inverse-Compton (IC)
reprocessed emission. 

The extreme blazar phenomenology, the variability and emission
mechanisms as well as the site of high energy production are some of the
topics that can be investigated by means of multi-frequency monitoring
of selected prototypical sources. The F-GAMMA program (Fermi-GST AGN
Multi-frequency Monitoring Alliance) is among the most comprehensive
attempts to understand the AGN physics through tracing the evolution of
the broad-band radio spectra of some 65 selected Fermi blazars over a
range spaning between 2.6 and 345 GHz at 12 frequency steps in total and
polarised intensity mode. It utilizes the Effelsberg 100-m, Pico Veleta
30-m and the APEX telescopes in a monthly monitoring fashion since
January 2007.

In this talk I will introduce the F-GAMMA program and then I will
summarise some of our recent studies: (a) The evaluation of the
correctness of the shock-in-jet model as the mechanism responsible for
the observed variability. (b) Suggest a simple generalised 2-component
system that can explain all the observed phenomenologies despite the
broadness of the sample parameter space. (c) Discuss the bias-free
Flux_radio - Flux_gamma correlation found at short-mm bands. (d) Show
how the cross-band correlation analysis can localize the high energy
emission site and (e) discuss the importance and the first results of
linear and circular polarisation variability. I will conclude discussing
the recent discovery of a new class of gamma-ray loud AGN: the Narrow
Line Seyfert 1s and their radio jet emission properties as those are
found through intensive multi-frequency monitoring campaigns.