The GLEAMing of the First Supermassive Black Holes

Abstract

We present the results of a new selection technique to identify powerful ($L_{500\mathrm{MHz}}>10^{27}$WHz${}^{-1}$) radio galaxies towards the end of the Epoch of Reionisation. Our method is based on the selection of bright radio sources showing radio spectral curvature at the lowest frequency ($\sim 100$MHz) combined with the traditional faintness in $K-$band for high redshift galaxies. This technique is only possible thanks to the Galactic and Extra-galactic All-sky Murchison wide-field Array (GLEAM) survey which provides us with 20 flux measurements across the $70-230$MHz range. For this pilot project, we focus on the GAMA 09 field to demonstrate our technique. We present the results of our follow-up campaign with the Very Large Telescope, Australian Telescope Compact Array and the Atacama Large Millimetre Array (ALMA) to locate the host galaxy and to determine its redshift. Of our four candidate high redshift sources, we find two powerful radio galaxies in the $1<z<3$ range, confirm one at $z=5.55$ and present a very tentative $z=10.15$ candidate. Their near-infrared and radio properties show that we are preferentially selecting some of the most radio luminous objects, hosted by massive galaxies very similar to powerful radio galaxies at $1<z<5$. Our new selection and follow-up technique for finding powerful radio galaxies at $z>5.5$ has a high $25-50\%$ success rate.

19 pages, 9 figures, published in PASA

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• New Radio-Loud QSOs at the end of the Re-ionisation Epoch
• Constraining the Radio Properties of the $z$=6.44 QSO VIK J2318$-$3113
• Comprehensive view on a $z\sim 6.5$ radio-loud QSO: from the radio to the optical/NIR to the X-ray band
• High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties
• A Search for Missing Radio Sources at $z\gtrsim 4$ Using Lyman Dropouts
• Building a Radio AGN Sample from Cosmic Morning -- The Radio High-Redshift Quasar Catalog (RHzQCat): I. Catalog from SDSS Quasars and Radio Surveys at $z>3$