EXIST: Surveying Black Holes from the Early Universe to Local Galaxies

The Energetic X-ray Imaging Survey Telescope (\textit{EXIST}) is proposed to survey the Universe for black holes on all scales and is a leading candidate to be the \textit{Black Hole Finder Probe} with three primary science goals: \textbf{1.} Detect and study cosmic gamma-ray bursts (GRBs) at high redshift to study stellar mass black hole formation and the epoch of re-ionization in the Early Universe. \textbf{2.} Conduct an unbiased hard X-ray survey for supermassive black holes in galactic nuclei to measure the fraction of those that are obscured and/or dormant to constrain the accretion luminosity of the Universe; and \textbf{3.} Study high energy transients, from stars to SMBHs, synoptic with ground and space temporal surveys. \textit{EXIST} would carry 3 instruments: a wide-field (90$^{\circ}$x70$^{\circ})$ high energy (5-600 keV) telescope (\textbf{HET}) to yield $<$20'' source positions; a 1.1m optical-infrared telescope (\textbf{IRT}) which images a $\sim $4'x4' field around the HET position simultaneously in 4 bands (0.3-2.1microns) and obtains low-res or high-res spectra and redshifts; and a focusing soft X-ray imager (\textbf{SXI}) for sensitive 0.1 --10 keV images (20' FoV and 15'' resolution) during both the 2y scanning mode and 3y followup pointings for imaging and spectra. \textit{EXIST} would serve a broad community of guest investigators following a proposed launch in 2017.