The Next Generation Virgo Cluster Survey. XV. The photometric redshift
  estimation for background sources
  The Next Generation Virgo Cluster Survey is an optical imaging survey
covering 104 deg^2 centered on the Virgo cluster. Currently, the complete
survey area has been observed in the u*giz-bands and one third in the r-band.
We present the photometric redshift estimation for the NGVS background sources.
After a dedicated data reduction, we perform accurate photometry, with special
attention to precise color measurements through point spread
function-homogenization. We then estimate the photometric redshifts with the Le
Phare and BPZ codes. We add a new prior which extends to iAB = 12.5 mag. When
using the u*griz-bands, our photometric redshifts for 15.5 \le i \lesssim 23
mag or zphot \lesssim 1 galaxies have a bias |\Delta z| < 0.02, less than 5%
outliers, and a scatter \sigma_{outl.rej.} and an individual error on zphot
that increase with magnitude (from 0.02 to 0.05 and from 0.03 to 0.10,
respectively). When using the u*giz-bands over the same magnitude and redshift
range, the lack of the r-band increases the uncertainties in the 0.3 \lesssim
zphot \lesssim 0.8 range (-0.05 < \Delta z < -0.02, \sigma_{outl.rej} ~ 0.06,
10-15% outliers, and zphot.err. ~ 0.15). We also present a joint analysis of
the photometric redshift accuracy as a function of redshift and magnitude. We
assess the quality of our photometric redshifts by comparison to spectroscopic
samples and by verifying that the angular auto- and cross-correlation function
w(\theta) of the entire NGVS photometric redshift sample across redshift bins
is in agreement with the expectations.
