We present the results of an infrared ( IR ) study of high-redshift galaxy clusters with the MIPS camera on board the Spitzer Space Telescope .
We have assembled a sample of 42 clusters from the Red-Sequence Cluster Survey-1 over the redshift range 0.3 < z < 1.0 and spanning an approximate range in mass of 10 ^ { 14 - 15 } M _ { \odot } .
We statistically measure the number of IR-luminous galaxies in clusters above a fixed inferred IR luminosity of 2 \times 10 ^ { 11 } M _ { \odot } , assuming a star forming galaxy template , per unit cluster mass and find it increases to higher redshift .
Fitting a simple power-law we measure evolution of ( 1 + z ) ^ { 5.1 \pm 1.9 } over the range 0.3 < z < 1.0 .
These results are tied to the adoption of a single star forming galaxy template ; the presence of AGN , and an evolution in their relative contribution to the mid-IR galaxy emission , will alter the overall number counts per cluster and their rate of evolution .
Under the star formation assumption we infer the approximate total SFR per unit cluster mass ( \Sigma SFR/M _ { \mathrm { cluster } } ) .
The evolution is similar , with \Sigma SFR/M _ { \mathrm { cluster } } \sim ( 1 + z ) ^ { 5.4 \pm 1.9 } .
We show that this can be accounted for by the evolution of the IR-bright field population over the same redshift range ; that is , the evolution can be attributed entirely to the change in the in-falling field galaxy population .
We show that the \Sigma SFR/M _ { \mathrm { cluster } } ( binned over all redshift ) decreases with increasing cluster mass with a slope ( \Sigma SFR/M _ { \mathrm { cluster } } \sim M _ { \mathrm { cluster } } ^ { -1.5 \pm 0.4 } ) consistent with the dependence of the stellar-to-total mass per unit cluster mass seen locally .
The inferred star formation seen here could produce \sim 5-10 % of the total stellar mass in massive clusters at z = 0 , but we can not constrain the descendant population , nor how rapidly the star-formation must shut-down once the galaxies have entered the cluster environment .
Finally , we show a clear decrease in the number of IR-bright galaxies per unit optical galaxy in the cluster cores , confirming star formation continues to avoid the highest density regions of the universe at z \sim 0.75 ( the average redshift of the high-redshift clusters ) .
While several previous studies appear to show enhanced star formation in high-redshift clusters relative to the field we note that these papers have not accounted for the overall increase in galaxy or dark matter density at the location of clusters .
Once this is done , clusters at z \sim 0.75 have the same or less star formation per unit mass or galaxy as the field .