The goal of this collaborative project is to continue an on-going and successful program of frequent monitoring of the variability in quasar continuum emission and the response of the characteristic broad emission lines to those variations. This provides a probe of the size of the emitting regions, their velocities via the line profiles, and allows an estimate of the mass of the central super-massive black hole. This "reverberation mapping" method is the primary way of measuring the masses of black holes in the central regions of active galaxies out to high redshifts.
Broader impacts of the work include training of undergraduate and graduate students, and postdocs. Public outreach includes involvement in the COSMOS high school summer science teaching program.
The main goal of this funded research project was to use the time-variability observed in active galactic nuclei to work out the structure of the central engines which generate their enormous non-stellar power. We have used the Kast spectrograph on the Lick 3-meter telescope to monitor the rapid time variations of fast-moving gas around the center of many active galactic nuclei, over the course of a year. In many cases we detected the time lag of the gas with respect to the central power source, which gives us the light-travel time between them. Thus we know the physical size of the gas region, and by measuring its velocity in orbit around the central black hole, we deduce the mass of the black hole inside each of these active galaxies, the fundamental parameter determining how the central engine works. In detail, we observe emission lines from more than one state of gas. So by measuring different lags for different gas in individual galactic nuclei, our spectroscopic monitoring has actually revealed direct evidence for the stratification of gas around the central engine. We have also used our detailed monitoring program to work out where the hottest dust grains reside in the central engine, as seen by their infrared radiation, which also lags behind the power output from the center, by typically several weeks to a few months.
