An ACA 1mm survey of HzRGs in the ELAIS-S1: survey description and first
  results
  Radio-emitting jets might be one of the main ingredients shaping the
evolution of massive galaxies in the Universe since early cosmic times.
However, identifying early radio active galactic nuclei (AGN) and confirming
this scenario has been hard to accomplish, with studies of samples of radio AGN
hosts at z>2 becoming routinely possible only recently. With the above in mind,
we have carried out a survey with the Atacama Compact Array (ACA, or Morita
Array) at 1.3 mm (rms=0.15 mJy) of 36 high-redshift radio AGN candidates found
within 3.9deg2 in the ELAIS-S1 field. The work presented here describes the
survey and showcases a preliminary set of results. The selection of the sample
was based on three criteria making use of infrared (IR) and radio fluxes only.
The criterion providing the highest selection rate of high-redshift sources
(86% at z>0.8) is one combining an IR colour cut and radio flux cut
(S(5.8um)/S(3.6um)>1.3 and S(1.4GHz)>1mJy). Among the sample of 36 sources, 16
show a millimetre (mm) detection. In eight of these cases, the emission has a
non-thermal origin. A zsp=1.58 object, with a mm detection of non-thermal
origin, shows a clear spatial offset between the jet-dominated mm continuum
emission and that of the host's molecular gas, as traced by serendipitously
detected CO(5-4) emission. Among the objects with serendipitous line detections
there is a source with a narrow jet-like region, as revealed by CS(6-5)
emission stretching 20kpc out of the host galaxy.
