Too big to be real? No depleted core in Holm 15A

Authors: Paolo Bonfini, Bililign T. Dullo, Alister W. Graham

Partially depleted cores, as measured by core-Sérsic model `break radii', are typically tens to a few hundred parsecs in size. Here we investigate the unusually large (R<sub>γ'=0.5</sub> = 4.57 kpc) depleted core recently reported for Holm 15A, the brightest cluster galaxy of Abell 85. We model the 1D light profile, and also the 2D image (using Galfit-Corsair, a tool for fitting the core-Sérsic model in 2D). We find good agreement between the 1D and 2D analyses, with minor discrepancies attributable to intrinsic ellipticity gradients. We show that a simple Sérsic profile (with a low index n and no depleted core) plus the known outer exponential `halo' provide a good description of the stellar distribution. We caution that while almost every galaxy light profile will have a radius where the negative logarithmic slope of the intensity profile γ' equals 0.5, this alone does not imply the presence of a partially depleted core within this radius.

• astro-ph
• ApJ paper