The Nature and Likely Redshift of GLEAM J0917-0012
  We previously reported a putative detection of a radio galaxy at z=10.15,
selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array
(GLEAM) survey. The redshift of this source, GLEAM J0917-0012, was based upon
three weakly detected molecular emission lines observed with the Atacama Large
Millimetre Array (ALMA). In order to confirm this result, we conducted deep
spectroscopic follow-up observations with ALMA and the Karl Jansky Very Large
Array (VLA). The ALMA observations targeted the same CO lines previously
reported in Band 3 (84-115GHz) and the VLA targeted the CO(4-3) and [CI(1-0)]
lines for an independent confirmation in Q-band (41 and 44GHz). Neither
observation detected any emission lines, removing support for our original
interpretation. Adding publicly available optical data from the Hyper
Suprime-Cam survey, WISE and Herschel Space Observatory in the infrared, as
well as <10GHz polarisation and 162MHz inter-planetary scintillation
observations, we model the physical and observational characteristics of GLEAM
J0917-0012 as a function of redshift. Comparing these predictions and
observational relations to the data, we are able to constrain its nature and
distance. We argue that if GLEAM J0917-0012 is at z<3 then it has an extremely
unusual nature, and that the more likely solution is that the source lies above
z=7.
