Program: GS-2013A-Q-36

The ionizing radiation emitted by a luminous quasar can, like a flashlight, illuminate hydrogen in its vicinity, allowing us to directly *image* dense filaments around galaxies and proto-galactic clouds, which are otherwise invisible because of negligible star formation. We propose to conduct deep narrow band Ly-alpha imaging of luminous quasars at z ~ 2 to detect this Ly-a fluorescence from the surrounding intergalactic and circumgalactic (CGM) medium. Our team has made the first definitive detections of this effect, and we have developed radiative transfer simulations in a cosmological setting for direct end-to-end comparison to our proposed observations. This novel technique compliments decades of effort using absorption-line techniques and will provide an ideal target list for future kinematic analysis of the CGM.