High resolution X-ray spectroscopy of Active Galactic Nuclei

Sam will focus his studies and research on Active Galactic Nuclei (AGN), and the ionised gas (the 'warm absorber') that lies in our line of sight to their central engine (generally thought to be an accreting supermassive black hole). The detailed analysis of the absorption features imprinted by the gas on the nuclear X-ray continuum, as well as of the emission lines generated in the gas, is a powerful diagnostic of the physical conditions of the environment surrounding the nuclear black hole, of the dynamics of the gas, its chemical composition and ionisation state. The gas is generally observed to be outflowing from the innermost regions of the AGN; the outflow rates are often comparable to, or even larger than, those of the matter accreting onto the black hole, and leading to the AGN powerful X-ray emission. This suggests that both outflow and accretion play a major role in the evolution of the black hole mass and of the AGN as a whole. The feedback mechanism associated with this may regulate star formation in the host galaxy, and may determine the known relationship between the mass of the black hole and that of the surrounding spheroid.

Sam is expected to become very familiar with AGN science and learn the techniques employed in the analysis of high-resolution X-ray spectra, with the aim to contribute to and to further our investigations in this topic. He will start on the analysis of data obtained recently with the XMM-Newton Reflection Grating Spectrometer (RGS) as part of a multiwavelength observing campaign of the Seyfert galaxy NGC7469. Sam will be part of the international collaboration responsible for the campaign and will have the opportunity to work with expert astronomers at the forefront of research in the field of AGN. Depending on the evolution of this initial project, Sam will investigate different facets of NGC7469 X-ray behaviour or turn to other targets, for example using archive XMM-Newton and Chandra data.