A spectral-timing approach to the study of AGN outflows

The Universe is structurally organized, from the smallest to the largest scales. Stars, stellar remnants, gas, dust, and dark matter, are gravitationally bound in large systems called galaxies. It is thought that a supermassive black hole (SMBH) resides in the center of each galaxy. Some galaxies show signs of nuclear activity related to accretion of material onto the SMBH. The central regions of the galaxies associated with this phenomenon are called Active Galactic Nuclei (AGN). AGN feedback is often evoked as the likely explanation for the observed connection between the SMBH and its host. Observations show the mass of the black hole to correlate with the velocity dispersion of stars in the bulge, and with the galaxy bulge mass, which suggests the growth and co-evolution of the SMBH and the galaxy to be somehow regulated by the AGN. To decide whether the outflows are responsible for this relationship, it is first necessary to quantify the energy transferred by the outflowing material onto the surrounding medium. Hence, characterizing the physical properties of the outflows and their contribution to AGN feedback is of crucial importance to the understanding of large-scale structure formation and evolution. In my thesis, I focus on the study of ionized outflows in the form of ‘winds’ by taking into account their combined spectral and temporal properties, by developing a novel method which allows us to study the response time of the ionized gas to changes in the continuum, and from this infer the physical properties of the gas.