# Supra-galactic Colour Patterns in Globular Cluster Systems

## TL;DR

This study uncovers large-scale, synchronized colour modulation patterns in globular cluster systems across multiple galaxies, suggesting a non-random formation process linked to early cosmic feedback mechanisms.

## Contribution

It provides the first evidence of supra-galactic colour patterns in globular clusters, indicating a synchronized formation process over large spatial and temporal scales.

## Key findings

- Detected colour modulation patterns in globular clusters across multiple galaxies.
- Confirmed patterns are real and not due to observational errors.
- Suggests globular clusters formed in a synchronized manner during early cosmic epochs.

## Abstract

An analysis of globular cluster systems associated with galaxies included in the Virgo and Fornax HST Advanced Camera Surveys reveals distinct (g-z) colour modulation patterns. These features appear on composite samples of globular clusters and, most evidently, in galaxies with absolute magnitudes Mg in the range from -20.2 to -19.2. These colour modulations are also detectable on some samples of globular clusters in the central galaxies NGC 1399 and NGC 4486 (and confirmed on data sets obtained with different instruments and photometric systems), as well as in other bright galaxies in these clusters. After discarding field contamination, photometric errors and statistical effects, we conclude that these supra-galactic colour patterns are real and reflect some previously unknown characteristic. These features suggest that the globular cluster formation process was not entirely stochastic but included a fraction of clusters that formed in a rather synchronized fashion over large spatial scales, and in a tentative time lapse of about 1.5 Gy at redshifts z between 2 and 4. We speculate that the putative mechanism leading to that synchronism may be associated with large scale feedback effects connected with violent star forming events and/or with super massive black holes.