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The intergalactic medium (IGM) is the dominant reservoir of baryons,delineates the large scale structure at low to moderate overdensities, andprovides gas from which galaxies form and evolve. Simulations of a Cold DarkMatter (CDM) dominated universe predict that the IGM is distributed in a cosmicweb of filaments, and that galaxies should form along and at the intersectionsof these filaments (Bond et al. 1994; Miralda-Escude et al. 1996). Whileobservations of QSO absorption lines and the large scale distribution ofgalaxies have confirmed the CDM paradigm, the cosmic web has never beenconfirmed by direct imaging. Here we report the Lyman-alpha blob 2 (LAB2) inSSA22, with the Cosmic Web Imager. This is an integral field spectrographoptimized for low surface brightness, extended emission. With 22 hours of totalsource exposure, CWI has revealed that LAB2 has extended Lyman-alpha emissionwhich is consistent with filaments. We perform tests to secure the robustnessof this result, which relies on data with modest signal-to-noise ratio. We havedeveloped a smoothing algorithm that permits visualization of data cube slicesalong image or spectral-image planes. With both raw and smoothed data cubes wedemonstrate that the filaments are kinematically associated with LAB2 anddisplay double-peaked profiles of optically thick Lyman-alpha emission. Theflux is 10 to 20x brighter than expected for the emission from the IGM but isconsistent with boosted fluorescence from a buried QSO or gravitation coolingradiation. Using emission models we infer a baryon mass in the filaments of atleast 1-4x10e11 Solar Mass, and the dark halo mass is at least 2x10e12 SolarMass. The spatial kinematic morphology is more consistent with inflow from thecosmic web than outflow. LAB2 and the surrounding gas have significant andcoaligned angular momentum, strengthening the case for their association.

IGM Emission Observations with the Cosmic Web Imager: II. Discovery of Extended, Kinematically-Linked Emission around SSA22 Lyman-alpha Blob 2