The Spatial Distributions of Red and Blue Globular Clusters in Major Dry Merger Remnants

TL;DR

This study uses high-resolution simulations to show that major dry mergers tend to flatten the radial density profiles of globular clusters, reducing differences between red and blue populations, which can inform galaxy merger histories.

Contribution

It demonstrates how dry mergers influence the radial distribution slopes of globular clusters, highlighting the dependence on initial profiles and merger parameters.

Findings

Dry mergers flatten GC density profiles.

Steeper initial profiles lead to more flattening.

Observed similar slopes suggest dry merger history.

Abstract

Using high-resolution N-body simulations, we examine whether a major dry merger mitigates the difference in the radial density distributions between red and blue globular clusters (GCs). To this end, we study the relation between the density slope of the GCs in merger progenitors and that in a merger remnant, when the density distribution is described by $n_{\rm GC}\propto r^{-\alpha}$. We also study how our results depend on the merger orbit and the size of the core radius of the initial GC density distribution. We find that a major dry merger makes the GC profile flatter, and the steeper initial GC profile leads to more significant flattening, especially if the initial slope is steeper than $\alpha\sim3.5$. Our result suggests that if there is a major dry merger of elliptical galaxies whose red GCs have a steeper radial profile than the blue GCs, as currently observed, and their slopes are steeper than $\alpha\sim3.5$, the difference in the slopes between two populations becomes smaller after dry mergers. Therefore, the observed slopes of red and blue GCs can be a diagnostic of the importance of dry merger. The current observational data show that the red and blue GCs have more comparable and shallower slopes in some luminous galaxies, which may indicate that they have experienced dry mergers.