IGM Emission Observations with the Cosmic Web Imager: II. Discovery of
  Extended, Kinematically-Linked Emission around SSA22 Lyman-alpha Blob 2
  The intergalactic medium (IGM) is the dominant reservoir of baryons,
delineates the large scale structure at low to moderate overdensities, and
provides gas from which galaxies form and evolve. Simulations of a Cold Dark
Matter (CDM) dominated universe predict that the IGM is distributed in a cosmic
web of filaments, and that galaxies should form along and at the intersections
of these filaments (Bond et al. 1994; Miralda-Escude et al. 1996). While
observations of QSO absorption lines and the large scale distribution of
galaxies have confirmed the CDM paradigm, the cosmic web has never been
confirmed by direct imaging. Here we report the Lyman-alpha blob 2 (LAB2) in
SSA22, with the Cosmic Web Imager. This is an integral field spectrograph
optimized for low surface brightness, extended emission. With 22 hours of total
source exposure, CWI has revealed that LAB2 has extended Lyman-alpha emission
which is consistent with filaments. We perform tests to secure the robustness
of this result, which relies on data with modest signal-to-noise ratio. We have
developed a smoothing algorithm that permits visualization of data cube slices
along image or spectral-image planes. With both raw and smoothed data cubes we
demonstrate that the filaments are kinematically associated with LAB2 and
display double-peaked profiles of optically thick Lyman-alpha emission. The
flux is 10 to 20x brighter than expected for the emission from the IGM but is
consistent with boosted fluorescence from a buried QSO or gravitation cooling
radiation. Using emission models we infer a baryon mass in the filaments of at
least 1-4x10e11 Solar Mass, and the dark halo mass is at least 2x10e12 Solar
Mass. The spatial kinematic morphology is more consistent with inflow from the
cosmic web than outflow. LAB2 and the surrounding gas have significant and
coaligned angular momentum, strengthening the case for their association.
