ar X iv : 0 80 5 . 28 97 v 1 [ as tr o - ph ] 1 9 M ay 2 00 8 VLA and VLBA Observations of the Highest

We present 8.4 GHz VLA A-array and 1.4 GHz VLBA results on the radio continuum emission from the highest redshift radio-loud quasar known to date, the z = 6.12 QSO J1427+3312. The VLA observations show an unresolved steep spectrum source with a flux density of 250 ± 20 μJy at 8.4 GHz and a spectral index value of α 1.4 = −1.1. The 1.4 GHz VLBA images reveal several continuum components with a total flux density of 1.778±0.109 mJy, which is consistent with the flux density measured with the VLA at 1.4 GHz. Each of these components is resolved with sizes of a few milliarcseconds, and intrinsic brightness temperatures on the order of 10 to 10 K. The physical characteristics as revealed in these observations suggest that this QSO may be a Compact Symmetric Object, with the two dominant components seen with the VLBA, which are separated by 31 mas (174 pc) and have intrinsic sizes of∼ 22−34pc, being the two radio lobes that are confined by the dense ISM. If indeed a CSO, then the estimated kinematic age of this radio AGN is only 10 yr. Subject headings: galaxies: individual (J1427+3312) — galaxies: active — galaxies: high-redshift — radio continuum: galaxies — techniques: interferometric now at: National Radio Astronomy Observatory, P. O. Box O, Socorro, NM, 87801, [email protected]