A Supermassive Black Hole That Wasn’t So Massive

GMOS-South image of the center of the Abell 85 galaxy cluster.

One sign of an extreme supermassive black hole at a galaxy’s core is a light deficit, the consequence of ejection of stars from the central region. The brightest cluster galaxy of Abell 85 had been identified as such an example, claimed to host one of the most massive black holes ever detected in the Universe at around 10¹¹M_Sun. Juan Madrid, then a Science Fellow at Gemini South, along with Carlos Donzelli (Observatorio Astronómico de Córdoba), used the spatial resolution of images obtained with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South to demonstrate that its mass was not so extreme. Data from their brief Director’s Discretionary Time program (seven minutes of observations) show the strong nuclear emission in the central kiloparsec – a light excess that may be due to a nuclear stellar disk. More information about this work is posted at the Gemini website, and full results are published in The Astrophysical Journal.