DEEP CFHT Y-BAND IMAGING OF VVDS-F22 FIELD. I. DATA PRODUCTS AND PHOTOMETRIC REDSHIFTS

We present our deep Y-band imaging data of a 2 square degree field within the F22 region of the VIMOS VLT Deep Survey. The observations were conducted using the WIRCam instrument mounted at the Canada–France–Hawaii Telescope (CFHT). The total on-sky time was 9 hr, distributed uniformly over 18 tiles. The scientific goals of the project are to select faint quasar candidates at redshift $z>2.2$ and constrain the photometric redshifts for quasars and galaxies. In this paper, we present the observation and the image reduction, as well as the photometric redshifts that we derived by combining our Y-band data with the CFHTLenS $u^{\ast }{g}^{\prime }{r}^{\prime }{i}^{\prime }{z}^{\prime }$ optical data and UKIDSS DXS JHK near-infrared data. With the J-band image as a reference, a total of ∼80,000 galaxies are detected in the final mosaic down to a Y-band $5\sigma$ point-source limiting depth of 22.86 mag. Compared with the ∼3500 spectroscopic redshifts, our photometric redshifts for galaxies with $z<1.5$ and $i^{\prime }\lesssim 24.0$ mag have a small systematic offset of $|\Delta z|\lesssim 0.2$, 1σ scatter $0.03<{\sigma }_{\Delta z}<0.06$, and less than 4.0% of catastrophic failures. We also compare with the CFHTLenS photometric redshifts and find that ours are more reliable at $z\gtrsim 0.6$ because of the inclusion of the near-infrared bands. In particular, including the Y-band data can improve the accuracy at $z\sim 1.0\text{--}2.0$ because the location of the 4000 Å break is better constrained. The Y-band images, the multiband photometry catalog, and the photometric redshifts are released at http://astro.pku.edu.cn/astro/data/DYI.html.