LBA observations for project V620 semester 2022OCTS

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Ultra-high-redshift radio galaxies (UHzRGs; z > 5) are unique tracers of supermassive black hole growth and massive galaxy formation in the early Universe. A novel UHzRG selection technique was developed that makes use of broadband data (70-230 MHz) from the MWA GLEAM survey. A total of 14 high-priority targets have been identified using this technique that also have very faint near-infrared K-band host galaxy magnitudes from deep VLT imaging. Here, we propose 2.3-GHz LBA observations of two of these new UHzRG candidates, GLEAM J1033 and GLEAM J1037. Both of these compact radio sources (largest angular sizes 0.9 and 2.6 arcsec) have K > 24 (AB) and are therefore excellent candidates for being at z > 5 and possibly within the epoch of reionisation. VLBI observations of GLEAM J1033 and J1037 will provide highly valuable information on the growth and evolution of powerful radio sources at potentially a very early cosmic epoch. In particular, by resolving the radio structures of both sources, we will obtain estimates for a number of properties of the radio jets, including the jet power, equipartition magnetic field strength and bulk Lorentz factor, and we will also constrain the black hole mass and accretion rate.