A ${\bf 1.4}$ deg${\bf ^2}$ blind survey for CII], CIII] and CIV at
  ${\bf z\sim0.7-1.5}$. I: nature, morphologies and equivalent widths
  While traditionally associated with active galactic nuclei (AGN), the
properties of the CII] ($\lambda=2326$\,{\AA}), CIII]
($\lambda,\lambda=1907,1909$\,{\AA}) and CIV ($\lambda,\lambda=1549,
1551$\,{\AA}) emission lines are still uncertain as large, unbiased samples of
sources are scarce. We present the first blind, statistical study of CII],
CIII] and CIV emitters at $z\sim0.68,1.05,1.53$, respectively, uniformly
selected down to a flux limit of $\sim4\times10^{-17}$ erg s$^{-1}$ cm$^{-1}$
through a narrow band survey covering an area of $\sim1.4$ deg$^2$ over COSMOS
and UDS. We detect 16 CII], 35 CIII] and 17 CIV emitters, whose nature we
investigate using optical colours as well as HST, X-ray, radio and far
infra-red data. We find that $z\sim0.7$ CII] emitters are consistent with a
mixture of blue (UV slope $\beta=-2.0\pm0.4$) star forming galaxies with disky
HST structure and AGN with Seyfert-like morphologies. Bright CII] emitters have
individual X-ray detections as well as high average black hole accretion rates
(BHAR) of $\sim0.1$ $M_{\odot}$ yr$^{-1}$. CIII] emitters at $z\sim1.05$ trace
a general population of SF galaxies, with $\beta=-0.8\pm1.1$, a variety of
optical morphologies, including isolated and interacting galaxies and low BHAR
($<0.02$ $M_{\odot}$ yr$^{-1}$). Our CIV emitters at $z\sim1.5$ are consistent
with young, blue quasars ($\beta\sim-1.9$) with point-like optical
morphologies, bright X-ray counterparts and large BHAR ($0.8$ $M_{\odot}$
yr$^{-1}$). We also find some surprising CII], CIII] and CIV emitters with
rest-frame equivalent widths which could be as large as $50-100$ {\AA}. AGN or
spatial offsets between the UV continuum stellar disk and the line emitting
regions may explain the large EW. These bright CII], CIII] and CIV emitters are
ideal candidates for spectroscopic follow up to fully unveil their nature.
