| It is thought that the immense energies associated with accretion of matter onto black holes in Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSOs) may "feedback," via intense photon flux or outward motion of gas, and affect certain properties of the host galaxy. In particular, AGN feedback may contribute to "quenching," or ceasing, of star formation by the expulsion or heating of cold gas, causing the host galaxy to evolve onto the red sequence (e.g., Di Matteo et al. 2005, Hopkins et al. 2006). I probe for the effects of feedback on the stellar populations of 60 X-ray-selected AGN hosts at a redshift of 1 in the Great Observatories Origins Deep Survey (GOODS) Southern field. Combining high spatial resolution optical imaging from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS), and high spatial resolution near infrared data from Keck Laser Guide Star Adaptive Optics (AO) and HST Near-Infrared Camera and Multi-Object Spectrograph (NICMOS), I test for the presence of young stars on sub-kiloparsec scales, independent of dust extinction. Testing for correlations between near-ultraviolet/optical (NUV -- R) colors and gradients and X-ray parameters such as hardness ratio and luminosity reveals new information about the nature of AGN-driven feedback. These AGN hosts display color gradients in rest-frame NUV -- R as far inward as ∼400 pc, suggesting stellar mixtures with nonuniform age distributions. There is little (< 0.3 mags) difference between the NUV -- R gradients of the obscured (hard in X-ray) sources and the unobscured (soft in X-ray) sources, suggesting that the unobscured sources are not increasingly quenched of star formation. I compare the NUV -- R colors of spiral galaxies that host AGN to non-active spirals, finding similar color gradients, but redder colors. These observations support the notion that unobscured intermediate-luminosity AGN hosts do not appear to be increasingly quenched of star formation relative to obscured sources.;These observations are meant to develop robust techniques for understanding AGN hosts at high spatial resolution. I present a new technique for constraining intrinsic color gradients in galaxies when a point spread function (PSF) is not well-constrained. Utilizing parametric 2-D fitting routines to compute aperture corrections, this method is more robust to PSF variation than most deconvolution methods.;Future adaptive optics instrumentation may deliver the spatial resolution required to resolve circumnuclear starbursting in AGN and faint hosts around bright QSOs at redshifts beyond 1, which may be helpful for testing other predictions of AGN evolution theory. Toward this end, for the second part of my thesis, I describe the use of a laboratory mock-up of the adaptive optics system for a 10-meter telescope to demonstrate diffraction-limited imaging with laser guide stars at visible wavelengths (710 nm). This laser tomographic AO system maintains 24--34% Strehl over a 45" field in R-band. I present new developments in open-loop wavefront sensing and calibration that will be important for laser guide star visible-light AO systems on 8--10 meter class telescopes. These experiments lend credence to development of high-order, visible-light AO instrumentation on 8--10 meter telescopes in the coming decade. |
