The bandpass of the WFCAM Z filter (0.83-0.925µm) was designed to provide a reasonable match to the effective wavelength of the SDSS z’ bandpass, but with a rectangular profile, and avoiding the atmospheric absorption band near 0.95µm. The specified WFCAM Z profile is shown in red. The array quantum efficiency is approximately flat over this wavelength range. The SDSS z’ bandpass is defined by the long-pass z’ filter and the falling q.e. of the CCDs towards longer wavelengths, multiplied by the atmospheric transmission. The normalised z’ system throughput is shown as the grey dash-dot line. The effective wavelengths of the WFCAM Z and SDSS z’ bandpasses are 0.876µm and 0.887µm, respectively (effective wavelength as defined by Schneider et al. 1993, ApJ, 264, 337).

 UKIDSS WFCAM Z filter profile

WFCAM Z filter. The red line plots the specified profile of the WFCAM Z filter, normalised to the peak transmission. The dash-dot grey line is the normalised system throughput for the SDSS z’ passband (Fan et al. (2001) AJ, 121, 31). The lilac line plots the atmospheric transmission (normalised to the continuum) for typical conditions.

(credit: UKIDSS website)