Guillaume Drouart (ICRAR/Curtin)

Guillaume Drouart Colloquium: Toward the first sample of radio powerful AGN in the EoR

Kensington Lecture Theatre/Online

Abstract

With the very recent discovery of radio luminous AGN at z>6, a new window of opportunity is finally opening in the study of the galaxy evolution at the end of the Epoch of Reionization. Our pilot programme in the 60 deg^2 GAMA-09 field uses a new selection technique taking advantage of the large frequency coverage of GLEAM by selecting compact, steep and curved sources at low-frequency (70-230MHz). Out of four candidates, one new powerful radio galaxy, 0856+0224, is confirmed at z=5.55, finally overtaking the z=5.2 20 year-old record for distant radio galaxies (albeit just falling short of the new recent z=5.7 record). Interestingly, 0856+0224 presents similarities with existing z<5 redshift samples, giving confidence in the success of our selection technique. Our recent progress on a second source, 0917-0012, thanks to the extensive multi-wavelength coverage from follow-up observations with ALMA and JVLA, supplemented with publicly available data, place this source at a promising z>5. I will also discuss the refinement of our selection technique over the full 1200 deg^2 sky area covered by the ESO VIKING near-infrared survey, leading to 55 new high-redshift candidates. This sample aims to provide us with the first statistically significant radio luminous active galactic nuclei sample at z > 6.5 during the Epoch of Reionization. The nature of radio selection presents the advantage of being insensitive to orientation-dependent obscuration, it allows us (i) to study simultaneously the co-evolution of the supermassive black hole and host galaxy and (ii) to enable the study of the IGM through the HI absorption line.