Wide-Field Multiband Photometry of Globular Cluster Systems in the Fornax Galaxy Cluster

TL;DR

This study provides deep, wide-field multiband photometry of globular cluster systems in the Fornax galaxy cluster, revealing bimodal color distributions, radial color gradients, and signs of ongoing galaxy interactions and mergers.

Contribution

It offers one of the deepest U-band studies of extragalactic GCs, with new insights into their spatial distribution and galaxy interaction evidence.

Findings

GC systems show bimodal color distributions in all examined colors.

Color gradients indicate bluer GCs at larger galactocentric radii.

Evidence of ongoing interactions and mergers in NGC 1399.

Abstract

We present wide-field multiband photometry of globular cluster (GC) systems in NGC 1399, NGC 1404, and NGC 1387 located at the central region of the Fornax galaxy cluster. Observation was carried out through U, B, V, and I bands, which marks one of the widest and deepest U-band studies on extragalactic GC systems. The present U-band photometry enables us to significantly reduce the contamination by a factor of two for faint sources (Vo~23.5). The main results based on some 2000 GC candidates around NGC 1399, NGC 1404, and NGC 1387 are as follows: (1) the GC system in each galaxy exhibits bimodal color distributions in all colors examined, but the shape of color histograms varies systematically depending on colors; (2) NGC 1399 shows that the mean colors of both blue and red GCs become bluer with increasing galactocentric radius; (3) NGC 1399 shows overabundance of GCs in the directions of NGC 1404 and NGC 1387, indicating their ongoing interactions; and (4) NGC 1399 also exhibits a ~0.5' offset between the center of the inner GC distribution and the galaxy's optical center, suggesting that NGC 1399 is not yet dynamically relaxed and may be undergoing merger events.