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Session 104 - Radio Galaxies, Radio Observations of AGN Jets & Outflows.
Display session, Saturday, January 10
Exhibit Hall,
The physical mechanism underlying observed emission line nebulae of high redshift radio galaxies still remains uncertain. Possible explanations of the gas motion include turbulent hydrodynamic interactions with radio jets, infall/outflow, and rotation. Additionally, models attempt to explain the highly ionized emission-line nebulae through photoionization by a central AGN and collisional ionization by shocks.
Adding more clues to the puzzle, we present Keck/LRIS spectra showing surprisingly extended high ionization emission with remarkable velocity structure associated with the radio galaxy MG 2144+1929. This object is the highest redshift galaxy (z=3.594) from the MIT/Greenbank 5 GHz radio survey and is the fifth highest redshift radio galaxy reported to date. Adopting a cosmology of H_0=50\ \rmkm\ s^-1Mpc^-1 and \rmq_0=0, we measure high ionization CIV and HeII emission spanning \sim140\ \rmkpc and a \rmLy\alpha nebula extending over \sim150\ \rmkpc. The emission nebulae are aligned with the radio axis and extend beyond the radio lobes. FWHM velocities reach \sim 1600\ \rmkm\ s^-1. The nebulae are spatially clumpy with multi-component velocity displacements up to \sim 1900\ \rmkm\ s^-1. The velocity fields of the three nebulae are dissimilar, suggesting that the emission is unlikely to be reflected quasar broad line emission but rather stems from turbulent emitting gas. These velocity structures are perhaps most consistent with a shock ionization picture; however, the CIV/HeII line ratio cannot be explained by current shock ionization models.
