Specific Frequencies and Luminosity Profiles of Cluster Galaxies and Intracluster Light in Abell 1689

TL;DR

This study analyzes the globular cluster populations and luminosity profiles of galaxies in Abell 1689, revealing their distribution, specific frequencies, and implications for intracluster light and supermassive black holes.

Contribution

It provides detailed measurements of globular cluster specific frequencies and luminosity profiles in Abell 1689, including the first decomposition of GCs into galaxy-associated and intracluster components.

Findings

ICL accounts for 11% of starlight in the field.

ICGCs constitute about 35% of the GCs.

The BCG has a large core radius of 3.8 kpc.

Abstract

We present magnitudes and profile fits for 180 galaxies in the central field of the massive lensing cluster Abell 1689 using very deep imaging with the ACS/HST in the F814W bandpass. Previous work revealed an exceptionally large number of globular clusters (GCs) in A1689 and mapped their number density distribution. We decompose this number density map into GCs associated with individual cluster galaxies and ICGCs (intracluster globular clusters) associated with the intracluster light (ICL). In all, we measure GC specific frequencies $S_N$ for 33 cluster members and the ICL. The relation between $S_N$ and galaxy magnitude is consistent with the trend observed in Virgo, although some intermediate luminosity galaxies scatter to $S_N>10$. We estimate the ICL makes up 11% of the starlight in this field, whereas the ICGCs account for $\sim\,$35% of the GCs, both consistent with predictions from simulations. Galaxies with higher $S_N$ values tend to be rounder, and there is a marginally significant trend of decreasing $S_N$ with increasing specific angular momenta $\lambda_R$. We also reevaluate the GC population in the A2744 Frontier Field, for which fewer than one-tenth as many GCs have been detected because of its larger distance. Finally, our core-S\'ersic fit to the light profile of the A1689 BCG implies a break radius of 3.8kpc, among the largest known; we discuss implications of the sizable core and extensive GC population for the supermassive black hole in light of scaling relations.