Globular Cluster Systems in Brightest Cluster Galaxies: A Near-Universal Luminosity Function?
Abstract
We present the first results from our HST Brightest Cluster Galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed luminosity function (LF) of the GCs down to the GCLF turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (log L > 10^7 L_Sun) we find small numbers of "superluminous" objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of UCDs (Ultra-Compact Dwarfs). Lastly, we find preliminary evidence that in the outer halo (R > 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L_0 ~ R^-0.2, while the LF dispersion remains nearly constant.
Cite
@article{arxiv.1410.6291,
title = {Globular Cluster Systems in Brightest Cluster Galaxies: A Near-Universal Luminosity Function?},
author = {William E. Harris and Warren Morningstar and Oleg Y. Gnedin and Heather O'Halloran and John P. Blakeslee and Bradley C. Whitmore and Patrick Cote and Douglas Geisler and Eric W. Peng and Jeremy Bailin and Barry Rothberg and Robert Cockcroft and Regina Barber DeGraaff},
journal= {arXiv preprint arXiv:1410.6291},
year = {2015}
}
Comments
To appear in Astrophysical Journal, December 2014