2016MNRAS.460.3861K

We present a Herschel/Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z=2-3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours (S_350/S250 and S_500/S350) of 250 µm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4σ overdensity of six SPIRE sources around 4.5 arcmin (∼2.2 Mpc) from a density peak of H α emitters at z=2.2. In the HS1700 field, we found a 5σ overdensity of eight SPIRE sources around 2.1 arcmin (∼1.0 Mpc) from a density peak of Lyman-break galaxies at z=2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 µm sources are concentrated 3 arcmin (∼1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 10^3–104 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ∼ 2-3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ∼ 2-3 protoclusters.