NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission

Understand

The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial.

• Background and contamination uncertainties present in the data of non-focusing observatories result in lower sensitivity to IC emission and a greater chance of false detection.
• We present 266ks NuSTAR observations of the Bullet cluster, detected from 3-30 keV.
• NuSTAR's unprecedented hard X-ray focusing capability largely eliminates confusion between diffuse IC and point sources; however, at the highest energies the background still dominates and must be well understood.