Infoscience

Journal article

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 two 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 hours, 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*g'r'i'z' optical data and UKIDSS DXS JHK near-infrared data. With J-band image as reference total similar to 80,000 galaxies are detected in the final mosaic down to Y-band 5 sigma point source limiting depth of 22.86 mag. Compared with the similar to 3500 spectroscopic redshifts, our photometric redshifts for galaxies with z < 1.5 and i'less than or similar to 24.0 mag have a small systematic offset of vertical bar Delta z vertical bar less than or similar to 0.2, 1 sigma scatter 0.03< (sigma)Delta(z) < 0.06, and less than 4.0% of catastrophic failures. We also compare to the CFHTLenS photometric redshifts, and find that ours are more reliable at z greater than or similar to 0.6 because of the inclusion of the near-infrared bands. In particular, including the Y-band data can improve the accuracy at z similar to 1.0-2.0 because the location of the 4000 angstrom-break is better constrained. The Y-band images, the multi-band photometry catalog and the photometric redshifts are released at http://astro.pku.edu.cn/astro/data/DYI.html.

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