H{alpha} fluxes in Cl J0023+0423B galaxies

Our 3{sigma} flux limits correspond to an SFR of 0.24h_100_^-2^M_{sun}_/yr, and our minimum reliable H{alpha}+[NII] equivalent width is greater than 10{AA}, demonstrating that near-infrared narrow-band imaging can sample the star-forming galaxy population in distant clusters. Comparison with spectroscopy shows that the number of false detections is low (9%+/-6%) and that our H{alpha} equivalent widths are correlated with spectroscopically determined [O II] equivalent widths.

A magnitude-limited spectroscopic survey conducted over the same area missed 70% of the star-forming galaxies and 65% of the integrated star formation. Using Hubble Space Telescope Wide Field Planetary Camera 2 Archive images, we fit Sersic profiles to all galaxies with significant narrow-band equivalent widths and find that equivalent width decreases as the steepness of galaxy profile increases.