Speaker
Description
High-redshift radio galaxies are vital laboratories for studying massive galaxy formation and evolution in the early Universe (review by Miley & De Breuck 2008). We have developed a new selection technique for finding these rare, powerful systems, making use of spectral curvature in the Murchison Widefield Array (MWA) 72-231 MHz GLEAM survey (Hurley-Walker et al. 2017; Franzen et al. 2021). In a pilot study of four sources in the 60 deg$^2$ GAMA-09 field, we discovered the second-most distant radio galaxy currently known (GLEAM J0856 at redshift z = 5.55; Drouart et al. 2020), with the possibility that a second source is also at z > 5 (GLEAM J0917; Drouart et al. 2021, submitted). While GLEAM offers excellent coverage of the low-frequency radio spectrum of both J0856 and J0917, we have combined these data with Low-Frequency Array (LOFAR) 34-66 MHz observations to better constrain the spectral curvature properties, search for and model a spectral turnover, and assess the accuracy of low-frequency flux density scales. By identifying the mechanism(s) responsible for a spectral turnover, we will gain new insights into the physical conditions at the end of, and possibly during, the Epoch of Reionisation.
