http://arxiv.org/abs/1709.04308
The Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) has been conducted over a 5-yr period at CFHT with the MegaCam instrument, totaling 450 nights of observations. The Wide Synoptic Survey is one component of the CFHTLS, covering 155 square degrees in four patches of 23 to 65 square degrees through the whole MegaCam filter set (u*, g’, r’, i’, z’) down to i’=24.5 (AB).
With the motivation of searching for high-redshift quasars at redshifts above 6.5, we extend the multi-wavelength CFHTLS-Wide data in the Y-band down to an AB magnitude of $\approx$ 22.5 (5-$\sigma$).
We observed the four CFHTLS-Wide fields (except one quarter of the W3 field) in the Y-band with the WIRCam instrument at CFHT. Each field was visited twice, at least 3 weeks apart. Each visit consisted of two dithered exposures. The images are reduced with the Elixir software used for the CFHTLS and modified to account for the properties of near IR data. Two series of image stacks are subsequently produced: 4-image stacks for each WIRCam pointing, and one square degree tiles matched to the format of the CFHTLS data release. Photometric calibration is performed on stars by fitting stellar spectra to their CFHTLS photometric data and extrapolating their Y-band magnitudes.
After corrections accounting for correlated noise, we measure a 5$\sigma$ AB point-source limiting magnitude of $\approx 22.4$ in an aperture diameter of 0.93″, over 130 square degrees.
S. Pipien, S. Basa, J. Cuby, et. al.
Thu, 14 Sep 17
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