Spitzer-selected z > 1.3 protocluster candidates in the LSST Deep Drilling Fields

We have identified 189 candidate z > 1.3 protoclusters and clusters in the LSST Deep Drilling Fields. This sample will enable the measurement of the metal enrichment and star formation history of clusters during their early assembly period through the direct measurement of the rate of supernovae identified through the LSST. The protocluster sample was selected from galaxy overdensities in a Spitzer/IRAC colour-selected sample using criteria that were optimized for protocluster purity using a realistic light-cone. Our tests reveal that 60-80 per cent of the identified candidates are likely to be genuine protoclusters or clusters, which is corroborated by a similar to 4 sigma stacked X-ray signal from these structures. We provide photometric redshift estimates for 47 candidates which exhibit strong peaks in the photo-z distribution of their candidate members. However, the lack of a photo-z peak does not mean a candidate is not genuine, since we find a stacked X-ray signal of similar significance from both the candidates that exhibit photo-z peaks and those that do not. Tests on the light-cone reveal that our pursuit of a pure sample of protoclusters results in that sample being highly incomplete (similar to 4 per cent) and heavily biased towards larger, richer, more massive, and more centrally concentrated protoclusters than the total protocluster population. Most (similar to 75 per cent) of the selected protoclusters are likely to have a maximum collapsed halo mass of between 10(13) and 10(14) M-circle dot, with only similar to 25 per cent likely to be collapsed clusters above 10(14) M-circle dot. However, the aforementioned bias ensures our sample is similar to 50 per cent complete for structures that have already collapsed into clusters more massive than 10(14) M-circle dot.