The Accretion History of AGN

Quantifying the evolution of active galaxies using a sample of 16,000 X-Ray detected sources from the Stripe82X, COSMOS, and GOODS surveys


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.

The Three Fields in the AHA Wedding Cake


GOODS unites extremely deep observations from NASA’s Great Observatories, Spitzer, Hubble, and Chandra, ESA’s Herschel and XMM-Newton, and from the most powerful groundbased facilities, to survey the distant universe to the faintest flux limits across the electromagnetic spectrum. The survey covers a total of roughly 320 square arcminutes in two fields centered on the Hubble Deep Field North and the Chandra Deep Field South.


The Cosmic Evolution Survey (COSMOS) is an astronomical survey designed to probe the formation and evolution of galaxies as a function of both cosmic time (redshift) and the local galaxy environment. The survey covers a 2 square degree equatorial field with spectroscopy and X-ray to radio imaging by most of the major space-based telescopes and a number of large ground based telescopes. Over 2 million galaxies are detected, spanning 75% of the age of the Universe.


The Stripe 82 X-ray survey covers 31 deg2 of the Sloan Digital Sky Survey (SDSS) Stripe 82 Legacy field. In total, 6181 unique X-ray sources are significantly detected with XMM-Newton (>5σ) and Chandra (>4.5σ). Due to the wide area of Stripe 82X and rich ancillary multi-wavelength data, including coadded SDSS photometry, mid-infrared WISE coverage, near-infrared coverage from UKIDSS and VHS, ultraviolet coverage from GALEX, radio coverage from FIRST, and far-infrared coverage from Herschel, as well as existing 50% optical spectroscopic completeness, w ∼ e are beginning to uncover rare objects, such as obscured high-luminosity AGN at high-redshift.

Science Goals

Obtain spectra

Obtain spectra for unidentified AGN and construct SEDs for all AGN in the GOODS, COSMOS and Stripe 82X surveys, using complementary selection techniques to minimize population biases, and using both spectroscopic and photometric redshifts to maximize statistics.

Constrain the key parameters

Constrain the key parameters of black hole growth over the past ~12 billion years, including the energy output as a function of wavelength and redshift, by developing a comprehensive population synthesis model that agrees with the GOODS+COSMOS+Stripe82X data.

Investigate the interplay

Investigate the interplay between star formation and black hole growth, especially in massive galaxies, using measures of stellar mass, star-formation rate, galaxy morphology, and clustering of both AGN and galaxies.