Radio Galaxy Zoo: host galaxies and radio morphologies derived from
  visual inspection
  We present results from the first twelve months of operation of Radio Galaxy
Zoo, which upon completion will enable visual inspection of over 170,000 radio
sources to determine the host galaxy of the radio emission and the radio
morphology. Radio Galaxy Zoo uses $1.4\,$GHz radio images from both the Faint
Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia
Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at
$3.4\,\mu$m from the {\it Wide-field Infrared Survey Explorer} (WISE) and at
$3.6\,\mu$m from the {\it Spitzer Space Telescope}. We present the early
analysis of the WISE mid-infrared colours of the host galaxies. For images in
which there is $>\,75\%$ consensus among the Radio Galaxy Zoo
cross-identifications, the project participants are as effective as the science
experts at identifying the host galaxies. The majority of the identified host
galaxies reside in the mid-infrared colour space dominated by elliptical
galaxies, quasi-stellar objects (QSOs), and luminous infrared radio galaxies
(LIRGs). We also find a distinct population of Radio Galaxy Zoo host galaxies
residing in a redder mid-infrared colour space consisting of star-forming
galaxies and/or dust-enhanced non star-forming galaxies consistent with a
scenario of merger-driven active galactic nuclei (AGN) formation. The
completion of the full Radio Galaxy Zoo project will measure the relative
populations of these hosts as a function of radio morphology and power while
providing an avenue for the identification of rare and extreme radio
structures. Currently, we are investigating candidates for radio galaxies with
extreme morphologies, such as giant radio galaxies, late-type host galaxies
with extended radio emission, and hybrid morphology radio sources.
