Wednesday Colloquium


"Magnetic dissipation behind extreme high-energy phenomena"

Krzysztof Nalewajko (NCAC, Warsaw)

Gamma-ray astronomy provides us with several types of extreme phenomena characterized by high apparent luminosity and rapid incoherent variability: flares in blazars, radio galaxies, pulsar winds, gamma-ray bursts. It seems plausible that all these events could be produced in relativistic magnetized outflows. In such environments, the most natural dissipation mechanism is relativistic magnetic reconnection. Significant progress in understanding relativistic reconnection has been made in recent years, however, many open questions remain to be answered.


"TBARadio galaxy scaling relations, radio galaxy remnants, and the nature of radio loud quasars"

Leith Godfrey ( Netherlands Institute for Radio Astronomy )

The first part of this presentation will be devoted to a discussion of the scaling relation between jet power and extended radio luminosity in radio galaxies. In principle, this scaling relation can be a powerful tool in statistical studies of radio galaxies and their energetic impact on the surroundings, provided the relation can be adequately calibrated. However, previously reported scaling relations, including those based on X-ray cavity measurements, are dominated by the mutual distance dependence of jet power and radio luminosity. After accounting for the mutual distance dependence, we find a significantly flatter relation than previously reported, and this result has strong implications for studies of radio mode feedback and radio galaxy physics. In the second part of the presentation, I will discuss our recent work on the remnant phase of radio galaxy evolution, and some of the ways in which the remnant population may be used as an effective tool to constrain radio galaxy physics. In particular, I will describe a search for remnant radio lobes associated with optically active AGN. Such objects are expected to exist if under certain conditions radio loud quasars transition to a radio quiet state. An evolutionary connection between radio loud and radio quiet quasars is predicted within certain classes of model, and our approach provides a clear test of such models.


"Absorption measure distribution: models vs observations "

Agata Różańska (Copernicus Astronomical Center, Warsaw )

We present how modelled absorption measure distribution (AMD) computed form the warm absorber under pressure equilibrium can explain the observed one in Mrk 509. AMD is constructed from observations of narrow absorption lines in radio-quiet AGN with warm absorbers. We study the properties of the warm absorber in Mrk~509 using recently published broad-band spectral energy distribution observed with different instruments. This spectrum is an input in our radiative transfer computations with full photoionisation treatment using {\sc titan} code. We found theoretical AMD which matches the observed one determined on the basis of 600 ks RGS XMM-Newton spectrum of Mrk~509. Our model puts strong constraints that the density of the warm absorber should be high enough to produce strong opacity jumps which are responsible for observed AMD dips. The excelent spectral resolution of ATHENA instrument will provide more poins in the observed AMD of many AGN and will allow for better test of our model.