A Supra-galactic Conundrum: The Globular Clusters Colour Pattern in Virgo Galaxies

TL;DR

This study reveals a consistent colour pattern in globular clusters across Virgo galaxies, suggesting an external influence affecting cluster formation on a large, possibly viral, scale.

Contribution

It provides new evidence of a universal globular cluster colour pattern in Virgo galaxies and extends the detection range to 30 Kpc in NGC 4486.

Findings

Pattern detected in 27 Virgo galaxies including NGC 4486

Pattern observable from 3 to 30 Kpc in NGC 4486

Supports hypothesis of an external, large-scale phenomenon influencing cluster formation

Abstract

The presence of systematic modulations in the colour distributions in composite samples of globular clusters associated with galaxies in the Virgo and Fornax clusters has been reported in a previous work. In this paper we focus on the 27 brightest galaxies in Virgo, and in particular on NGC 4486, the dominant system in terms of globular cluster population. The new analysis includes $\sim$7600 cluster candidates brighter than g =24.5 (or T1$\sim$ 23.70). The results indicate the presence of the characteristic Virgo pattern in these galaxies and that this pattern is detectable over a galactocentric range from 3 to 30 Kpc in N GC 4486. This finding gives more support to the idea that the pattern has been the result of an external, still not identified phenomenon, capable of synchronizing the cluster formation in a kind of viral process, and on supra-galactic scales (also having, presumably, an impact on the overall star formation history in the entire Virgo cluster).