Integral field spectroscopy of radio galaxy B2 0902+34

We have used the Visible Integral-field Replicable Unit Spectrograph Prototype (VIRUS-P), a new Integral Field Unit (IFU) Spectrograph, to study the spatially and spectrally resolved Lyman-[Greek small letter alpha] emission line structure in the radio galaxy B2 0902+34 at z [similar to] 3.4. VIRUS-P has a large field of view (3.2 sq. arcmin) and is very sensitive to low surface brightness emission. A halo of Ly [Greek small letter alpha] emission with velocity dispersion of [similar to] 600km s⁻¹ extends to 100 kpc, larger than previously detected with narrowband imaging and longslit spectroscopy. A newly discovered blue emission feature appears in the southwest with a velocity separation of [similar to] −700 km s⁻¹. We interpret this emission feature as the far side ionization cone with central infall while the brighter, more circularly distributed, and distinct kinematic component is the near side ionization cone. We present a simple model which reproduces the optical spectroscopic and radio data. We have also made the first optical detection of the neutral hydrogen (HI) absorption feature presented in earlier radio data. Lastly, we have searched the surrounding 3.2 sq. arcmin for companion galaxies. To a flux level of [similar to] 7×10⁻¹⁷ erg s⁻¹ cm⁻², we detect one possible companion in Lyman-[Greek small letter alpha]. We interpret the system as a proto-giant elliptical galaxy in a protocluster still in the act of mass accumulation.