BALSims: a Spectral Synthesis Approach to Understanding Broad Absorption Line Quasar Outflows

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

A longstanding problem in astrophysics is to understand how galaxies form and develop throughout their lifetimes. Such understanding is necessary to uncover how our Universe evolved and to gain insight into the origin of our own Milky Way Galaxy. One important aspect of understanding galaxy formation and evolution is to study supermassive black holes at the centers of galaxies and how these black holes interact with their host galaxies. Observational evidence suggests that black holes and galaxies evolve together. This evidence includes the tightness of the correlation between the black hole mass and galaxy bulge properties and the similar history of black hole growth and star formation. This evidence is supported by theoretical arguments. Black holes in their active phase emit more than enough energy to unbind the host galaxies' bulge, and in their non-active phase should be present in the centers of most present-day galaxies. As a consequence, many models for galaxy formation include a unspecified process by which a fraction of the energy released in the region surrounding the black hole contributes to the galaxy formation environment. This interaction is generically known as "feedback," and the mechanism by which the black hole acts on the host galaxy remains a mystery. This project uses a novel spectral synthesis and statistical approach to build the tools needed to constrain the key parameter characterizing one type of feedback. In addition, the project activities will directly contribute to the training of young scientists, including undergraduate students, in techniques of spectral and statistical analysis. The PI will develop and teach a course, directed toward advanced undergraduate and graduate students, on machine learning and statistical methods, some of which will be used in this project. The PI will bring the results of this research to the citizens of Oklahoma through participation in the OU speakers program. This research effort will constrain the key parameter characterizing quasar mode feedback: the ratio of the kinetic luminosity to bolometric luminosity, in the SDSS broad absorption line quasars as a whole. In addition, the carefully-phased research program addresses related scientific questions at each check point. These include the location and nature of feedback interactions, a search for and evaluation of absorption-line spectral diagnostics, and constraints of key outflow physical parameters, including column density, ionization parameter, and covering fraction. This research project will yield insights into the physics of quasar outflows, and measurements of key parameters that will be valuable to a wide variety of researchers. These include scientists who are interested in on-going interactions potentially occurring in infrared-loud quasars, data analysts who use spectral diagnostics to infer physical conditions from spectra of individual objects, and theorists who need observational constraints to develop their hydromagnetic wind models, as well as providing an assessment of the viability of quasar-mode feedback for galaxy evolution models.