Star formation in the XMMU J2235.3−2557 galaxy cluster at z= 1.39

We present the first results of a narrow-band photometric study of the massive galaxy cluster XMMU J2235.3−2557 at z= 1.39. We obtained deep H narrow-band imaging with the Near InfraRed Imager and Spectrometer on Gemini North, corresponding to Hα emission at the cluster's redshift. Our sample consists of 82 galaxies within a radius of ∼500 kpc, 10 of which are spectroscopically confirmed cluster m...