The turbulent life of NGC 4696 as told by its globular cluster system

Context. Globular clusters (GCs) are remarkable witnesses of their host galaxy's interaction and merger history. Aims. Our aim is to perform the photometric analysis of the globular cluster system (GCS) of the giant elliptical NGC 4696, which is the brightest member of Centaurus, a rich and dynamically young galaxy cluster. Methods. We obtained deep Magellan 6.5 m/MegaCam (g', r', i') photometry, with which we identified a sample of 3818 stellar clusters around NGC 4696 that were analyzed in the context of possible interactions and its assembly history. Results. After carefully modeling and subtracting the galaxy light, we used selection criteria based on the shape, colors, and magnitudes to identify GC candidates. We find a number of features that indicate a disturbed GCS that points toward a complex evolution with other neighboring members of Centaurus. Formally, two subpopulations could be found at (g'‑i')₀ = 0.763 ± 0.004 and (g'‑i')₀ = 1.012 ± 0.004. Moreover, the color distribution does not show the presence of a significant blue tilt, but it presents a trend with the radius, where at small galactocentric distances a unimodal distribution is preferable to a bimodal one, suggesting the presence of an intermediate GC population. Besides the color distribution, the metallicity distribution also shows a bimodal trend, with peaks at [Fe/H]= ‑ 1.363 ± 0.010 and [Fe/H]= ‑ 0.488 ± 0.012. The radial density profiles show different slopes for the blue and red populations and the azimuthal distributions are well fitted by an asymmetrical sinusoidal function, with peaks projecting toward two nearby galaxies, NGC 4696B and NGC 4709, indicating past interactions among these three galaxies. Finally, we derived a GC specific frequency of S_N = 6.8 ± 0.9, in good agreement with the values obtained for other giant ellipticals and with previously estimated S_N of NGC 4696. Conclusions. All these results point toward a complex GCS, strongly influenced by the interaction history of NGC 4696 with the other galaxies of the Centaurus cluster. In a future work, the spectroscopic follow-up of the GC candidates analyzed in this study and broadening the photometric baseline will allow us to highlight the formation and evolution of the entire Centaurus cluster. ⋆ This paper includes data gathered with the 6.5 meter Magellan Telescope located at Las Campanas Observatory, Chile, and obtained with MegaCam (McLeod et al. 2006). The data products are produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.