2003ApJ...586..735T

An Abell cluster, A2152, was recently found to be forming a cluster-cluster system with another, more distant cluster whose core is almost perfectly aligned with that of A2152. We discuss the detectability of microlensing events where a single star in the source cluster behind A2152 is extremely magnified by an intracluster compact object in A2152. We show that a search with an 8 m class telescope with a wide field of view, such as the Subaru/Suprime-Cam, can probe intracluster compact objects with a wide mass range of m_co∼10^–5to10¹⁰M_☉, including ranges that have not yet been constrained by any past observations. We expect that the event rate is more biased than the foreground cluster (A2152), which would be a unique signature of microlensing, making this experiment particularly powerful. The sensitivity of this experiment for the mass fraction of compact objects would be 1%-10% in the total dark matter of the cluster, which is roughly constant against m_co, with a reasonable telescope time for large telescopes (∼10 nights). Therefore, any compact objects in this mass range can be detected or rejected as the dominant component of the dark matter. About 10 events are expected if 20% of the cluster mass is in a form of compact objects with M∼1M_☉, as claimed by the MACHO collaboration for the Milky Way halo. Other possibly detectable targets include intracluster stars stripped by galaxy interactions, and hypothetical very massive black holes (M≳100M_☉) produced as remnants of the first-generation stars, which might be responsible for the recently reported excess of the cosmic infrared background radiation that seems impossible to explain by normal galactic light.