Collaborative Research: A Comprehensive Picture of Black Hole Growth Over Cosmic Time Using Multi-wavelength Population Synthesis

University Of Maryland Baltimore County, Baltimore MD

Investigators

Abstract

Black holes form when gravity pulls enormous amounts of matter into a small enough volume. Predicted by Einstein's Theory of General Relativity, they were first detected in astronomical observations of a special kind of galaxy called an "active galaxy"---distinguished by the fact that a very big black hole at its center is growing at a rapid rate and radiating enough light to heat the entire galaxy. From detailed measurements of that light in thousands of active galaxies, the investigators will learn when and where these black holes grew over the past 13 billion years of cosmic time. They will also connect that growth to measurements of the black hole masses at different epochs in order to form a comprehensive understanding of how and when black holes grew and how much energy was radiated into the galaxy as a result. This in turn supplies a vital ingredient to theorists' models of how galaxies like our own Milky Way formed and evolved. This project will advance discovery while promoting teaching, training, learning and excellence through a collaboration with the Meyerhoff Scholars program at the University of Maryland, Baltimore County. This proposal will identify up to 16,000 active galaxies in three surveys (called GOODS, COSMOS, and Stripe 82X), which have complementary combinations of depth (sensitivity) and area on the sky. The active galaxies will be identified by the amount of X-ray light they emit. Their distances will be measured using optical and infrared spectroscopic observations at large telescopes to determine the redshift (i.e., the wavelength shift of atomic emission or absorption lines) of a large fraction of the active galaxies. For the rest, the investigators will estimate redshifts by analyzing the total infrared, optical, and ultraviolet light that they emit. Catalogs listing the X-ray, infrared, and optical brightness of each active galaxy will be made publicly available, along with their redshifts, so that anyone can mine the data to answer other astronomical questions. In this project, the investigators will analyze the overall spectral energy distribution of each active galaxy to deduce its dust and gas content. For selected subsets of data, the investigators will measure key characteristics like black hole mass, luminosity, amount of dust and gas (important for understanding whether any light is occluded), black hole growth rate, and the number of other galaxies near each active galaxy. The investigators will combine these measurements to model the growth of black holes over time, constrained by the data acquired. The investigators will also search for evidence of the interplay between black hole growth at the center of the active galaxy and star formation throughout the active galaxy; this will be most apparent in massive galaxies, like our own Milky Way. All these investigations will be published and made openly available to everyone.