2MASS Photometric Redshift catalog: a comprehensive three-dimensional
  census of the whole sky
  Key cosmological applications require the three-dimensional galaxy
distribution on the entire celestial sphere. These include measuring the
gravitational pull on the Local Group, estimating the large-scale bulk flow and
testing the Copernican principle. However, the largest all-sky redshift surveys
-- the 2MRS and IRAS PSCz -- have median redshifts of only z=0.03 and sample
the very local Universe. There exist all-sky galaxy catalogs reaching much
deeper -- SuperCOSMOS in the optical, 2MASS in the near-IR and WISE in the
mid-IR -- but these lack complete redshift information. At present, the only
rapid way towards larger 3D catalogs covering the whole sky is through
photometric redshift techniques. In this paper we present the 2MASS Photometric
Redshift catalog (2MPZ) containing 1 million galaxies, constructed by
cross-matching 2MASS XSC, WISE and SuperCOSMOS all-sky samples and employing
the artificial neural network approach (the ANNz algorithm), trained on such
redshift surveys as SDSS, 6dFGS and 2dFGRS. The derived photometric redshifts
have errors nearly independent of distance, with an all-sky accuracy of
sigma_z=0.015 and a very small percentage of outliers. In this way, we obtain
redshift estimates with a typical precision of 12% for all the 2MASS XSC
galaxies that lack spectroscopy. In addition, we have made an early effort
towards probing the entire 3D sky beyond 2MASS, by pairing up WISE with
SuperCOSMOS and training the ANNz on GAMA redshift data reaching currently to
z_med~0.2. This has yielded photo-z accuracies comparable to those in the 2MPZ.
These all-sky photo-z catalogs, with a median z~0.1 for the 2MPZ, and
significantly deeper for future WISE-based samples, will be the largest and
most complete of their kind for the foreseeable future.
