We cross-match the two currently largest all-sky photometric catalogs , mid-infrared WISE and SuperCOSMOS scans of UKST/POSS-II photographic plates , to obtain a new galaxy sample that covers 3 \pi steradians .
In order to characterize and purify the extragalactic dataset , we use external GAMA and SDSS spectroscopic information to define quasar and star loci in multicolor space , aiding the removal of contamination from our extended-source catalog .
After appropriate data cleaning we obtain a deep wide-angle galaxy sample that is approximately 95 % pure and 90 % complete at high Galactic latitudes .
The catalog contains close to 20 million galaxies over almost 70 % of the sky , outside the Zone of Avoidance and other confused regions , with a mean surface density of over 650 sources per square degree .
Using multiwavelength information from two optical and two mid-IR photometric bands , we derive photometric redshifts for all the galaxies in the catalog , using the ANN z framework trained on the final GAMA-II spectroscopic data .
Our sample has a median redshift of z _ { \mathrm { med } } = 0.2 but with a broad \mathrm { d } N / \mathrm { d } z reaching up to z > 0.4 .
The photometric redshifts have a mean bias of | \delta z| \sim 10 ^ { -3 } , normalized scatter of \sigma _ { z } = 0.033 and less than 3 % outliers beyond 3 \sigma _ { z } .
Comparison with external datasets shows no significant variation of photo- z quality with sky position .
Together with the overall statistics , we also provide a more detailed analysis of photometric redshift accuracy as a function of magnitudes and colors .
The final catalog is appropriate for ‘ all-sky ’ 3D cosmology to unprecedented depths , in particular through cross-correlations with other large-area surveys .
It should also be useful for source pre-selection and identification in forthcoming surveys such as TAIPAN or WALLABY .