Astronomers using the Magellan Telescopes in Chile have conducted photometric observations of the giant elliptical galaxy NGC 4696, revealing a sophisticated globular cluster system within it. Published on June 12 in the pre-print server arXiv, Athe findings highlight NGC 4696 as a complex host of globular clusters.
Located about 145 million light years away, NGC 4696 is the brightest galaxy in the Centaurus Cluster. It spans approximately 4.5 by 3.2 arcminutes with a heliocentric velocity of about 2,958 km/s. Previous studies of NGC 4696 have identified a filamentary structure crossing its central region, possibly indicating past merger activity or material acquisition through ram-pressure stripping from nearby NGC 4696B.
Investigating the globular clusters (GCs) in and around NGC 4696 offers insights into its evolutionary history. Led by Sara Federle from the Andrés Bello National University in Chile, astronomers analyzed the galaxy’s globular cluster system (GCS) using deep Magellan 6.5m/MegaCam (g′, r′, i′) photometry.
The team initially identified 3,973 globular cluster candidates, narrowing down to 3,818 GC candidates through a two-color selection process. Analysis of these candidates revealed a disturbed GCS, suggesting a complex evolutionary path influenced by neighboring members of the Centaurus Cluster.
NGC 4696’s GCS exhibits a bimodal color distribution, with peaks at 0.763 mag (blue) and 1.012 mag (red), separated by approximately 0.905 mag. Despite lacking a significant blue tilt—a phenomenon where bluer clusters become redder with increasing luminosity—the GCS shows radial trends. Closer to the galaxy’s center, a unimodal color distribution prevails, hinting at the presence of an intermediate GC population.
Moreover, the study found a bimodal metallicity distribution within the GCS and noted distinct radial density profiles for the blue and red GC populations. Azimuthal distributions of total, red, and blue GC candidates followed an asymmetrical sinusoidal pattern, implying interactions between NGC 4696 and its neighboring galaxies have shaped its GCS.
In conclusion, these findings underscore the complex nature of NGC 4696’s GCS, influenced significantly by its interaction history with other galaxies in the Centaurus cluster.
