Non-detection of M60-UCD1 in Quasi-simultaneous X-Ray and Radio Observations

Abstract Simultaneous detection in X-rays and radio, following the proportionality implied by the “fundamental plane of black hole activity,” can indicate the presence of an accreting black hole (BH), allowing a rough estimate of its mass. We used the XMM-Newton satellite and the Karl G. Jansky Very Large Array to perform quasi-simultaneous observations (within 24 hr) of the ultra-compact dwarf galaxy M60-UCD1, where the presence of a supermassive BH was inferred from stellar dynamics. The galaxy was not detected in either the X-ray or the radio band. We used the fundamental plane of BH activity to set constraints on the mass of any BH that might reside in its nucleus.