Noor Md Said (University of Tasmania/CSIRO Astronomy and Space Science)

Colloquium: Intraday Variability of Active Galaxies

Online

Abstract

In this work I have undertaken a detailed investigation of the BL Lac object: PKS B1144−379. This project utilised high-cadence flux density monitoring of interstellar scintillation with the University of Tasmania Ceduna 30m radio telescope at a frequency of 6.7 GHz. A complementary kinematic study of the sub parsec-scale jet of PKS B1144−379 has been undertaken, using 8.6 GHz Very Long Baseline Interferometry (VLBI) data. The centimetre wavelength radio flux density of this source is known to vary on a range of timescales from a few days up to several months. The rapid (timescales of less than a day), apparent variability of this compact extragalactic radio source at radio wavelength is known as intraday variability (IDV). The current investigation shows conclusively that the rapid variability is the result of a propagation effect known as interstellar scintillation (ISS), which originates in the inhomogeneous interstellar medium (ISM). On the other hand, the long-term variability (months to years) suggests that the source also exhibits substantial intrinsic evolution.