Using three newly identified galaxy clusters at z \sim 1 ( photometric redshift ) we measure the evolution of the galaxies within clusters from high redshift to the present day by studying the growth of the red cluster sequence .
The clusters are located in the Spitzer Infrared Array Camera ( IRAC ) Dark Field , an extremely deep mid-infrared survey near the north ecliptic pole with photometry in 18 total bands from X-ray through far-IR .
Two of the candidate clusters are additionally detected as extended emission in matching Chandra data in the survey area allowing us to measure their masses to be M _ { 500 } = 6.2 \pm 1.0 \times 10 ^ { 13 } and 3.6 \pm 1.1 \times 10 ^ { 13 } M _ { \odot } .
For all three clusters we create a composite color magnitude diagram in rest-frame B-K using our deep HST and Spitzer imaging .
By comparing the fraction of low luminosity member galaxies on the composite red sequence with the corresponding population in local clusters at z = 0.1 taken from the COSMOS survey , we examine the effect of a galaxy ’ s mass on its evolution .
We find a deficit of faint galaxies on the red sequence in our z \sim 1 clusters which implies that more massive galaxies have evolved in clusters faster than less massive galaxies , and that the less massive galaxies are still forming stars in clusters such that they have not yet settled onto the red sequence .