The HectoMAP Cluster Survey - II. X-ray Clusters

We apply a friends-of-friends algorithm to the HectoMAP redshift survey and cross-identify associated X-ray emission in the ROSAT All-Sky Survey data (RASS). The resulting flux limited catalog of X-ray cluster survey is complete to a limiting flux of $\sim 3\times {10}^{-13}$ erg s${}^{-1}$ cm${}^{-2}$ and includes 15 clusters (7 newly discovered) with redshift $z\le 0.4$. HectoMAP is a dense survey ($\sim 1200$ galaxies deg${}^{-2}$) that provides $\sim 50$ members (median) in each X-ray cluster. We provide redshifts for the 1036 cluster members. Subaru/Hyper Suprime-Cam imaging covers three of the X-ray systems and confirms that they are impressive clusters. The HectoMAP X-ray clusters have an $L_X-{\sigma }_{cl}$ scaling relation similar to that of known massive X-ray clusters. The HectoMAP X-ray cluster sample predicts $\sim 12000 \pm3000$ detectable X-ray clusters in the RASS to the limiting flux, comparable with previous estimates.