Emission-lines from AGN&Starbursts: new steps to understanding their message

University Of Kentucky Research Foundation, Lexington KY

Investigators

Abstract

Much of modern astrophysics involves the interaction of electromagnetic radiation (light) with diffuse clouds of gas around stars, in galaxies and in the spaces between them. The radiation interacts with the atoms in the gas, heats the gas and sometimes ionizes and excites the atoms. The gas then emits light which, in turn, interacts with the gas. The detailed physical processes involved in these interactions are enormously complex and vary with the gas' temperature, density and chemical abundance. Understanding these processes and their interplay with the radiation allows astrophysicists to deduce the physical conditions in the gas clouds and the characteristics of the source of the radiation. Dr. Ferland is one of the world's experts in the study of the interplay of light and ionized gas and for thirty years he has been developing an open-source, publicly-available computer simulation tool called "Cloudy." Cloudy is used by hundreds of astronomers and astrophysicists in studies of diverse regions from star-forming regions to the light-emitting regions surrounding and excited by the supermassive black holes at the centers of active galaxies (Active Galactic Nuclei or AGN) and quasars. Cloudy has been used in the training and research of several generations of students and young researchers. This award will support a major upgrade of the Cloudy code that will improve its performance and range of applicability. The upgrade will potentially allow it to be used in simulations of gas in dense plasmas such as star-forming regions and will allow better calculation of the emission of light from gas near the heart of quasars. This is a time of unprecedented discovery in understanding the central regions of Active Galactic Nuclei and Starburst galaxies across the electromagnetic spectrum. Reverberation mapping of the Broad Lined Region, using optical H I recombination lines at low redshift, and collisionally excited lines at high redshift, have led to catalogs of supermassive black hole masses. These in turn make possible investigations of key questions such as the evolution of black hole mass, the role of AGN feedback, and the interplay between the evolution of the black hole and surrounding galaxy. The Atacama Large Millimeter/Sub-millimeter Array (ALMA) makes it possible to routinely study radio recombination lines from both AGN and Starburst galaxies, probing sources of ionizing radiation in dust-shrouded regions. ALMA can further probe molecular emission from both star-forming regions and the AGN molecular torus. This project will develop the theoretical tools needed to understand these emission-line observations and incorporate them into Cloudy, which has been designed to solve these plasma, chemistry, radiation transport, and dynamics problems simultaneously and self consistently, building from the foundation of individual atomic and molecular processes. The advances to be undertaken are motivated by recent discussions with the dense plasma / magnetic fusion communities. Methods and data they have developed will dramatically improve the numerical simulations at surprisingly low cost. These significantly improved simulations will be applied to models of the BLR, star-forming regions,and to associated molecular regions.