Outflows and AGN in the Nuclei of Merging Galaxies, Viewed with Laser Guide Star Adaptive Optics

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

Quasars are the most luminous objects in the universe. The active galactic nucleus (AGN) that is the quasar's powerhouse can outshine its entire host galaxy. In the more than fifty years since their discovery, a picture has emerged of a quasar as a supermassive black hole residing at or near the center of a large galaxy. Interstellar gas in the galaxy, perhaps the residue of stars disrupted by tidal forces as they orbit close to the black hole, falls into the black hole and in doing so is heated to very high temperatures and emits copious radiation over a wide range of wavelengths. Along with the gas inflow, it is also clear that quasars drive gas out of the nuclear region. An outstanding question in the evolution of galaxies is to what extent the outflow from a quasar expels the interstellar medium, thereby quenching star formation in the host galaxy. This effect could have a strong influence on the development of galaxies at early times in the universe. This project will use newly-developed imaging and spectroscopic techniques to study nearby active galaxies in fine detail to gain insights as to how and from where the outflow is driven. It will also study a sub-sample of active galaxies that may have double active nuclei at their centers. In addition, it will contribute to an established workforce development program on Maui and a teacher training program in California. Multiple lines of evidence suggest that quasars in the early universe drive massive galactic outflows that expel much of the interstellar medium in their host galaxies. These outflows are needed to quench star formation, limit black hole accretion, and give rise to observed relationships between the central black hole?s mass and properties of the galaxy's bulge. Without them, it is difficult to explain the old stellar population and low gas content of local "red and dead" massive galaxies, as well as their steeply declining number at high masses. For high-redshift galaxies it is difficult to study outflow processes in detail, because the galaxies have small apparent sizes and faint fluxes. This project will study the physical processes of nuclear outflows for nearby quasars and luminous infrared galaxies (0.01 < z < 0.15), using laser guide star adaptive optics coupled with integral field spectrographs which can map emission and absorption lines on scales of 10 - 100 pc in the host galaxy. The outflow characteristics thereby deduced from observations in the near-infrared will be compared to those at other wavelengths, including molecular observations by the Herschel satellite, ALMA, CARMA, and the SMA, and visible observations with integral field spectrographs such as Gemini's GMOS instrument. The project will also include observations of active galactic nuclei from the Sloan Digital Sky Survey with dual [O III] emission lines at 0.2 < z < 0.6 to identify outflows and distinguish them from dual active nuclei.