Mock Observations of Blue Stragglers in Globular Cluster Models

TL;DR

This study uses artificial models of globular clusters to analyze blue straggler populations, comparing observational methods and cluster properties to understand their formation and evolution.

Contribution

It introduces a comparison of blue straggler selection criteria and confirms the overestimation of their lifetimes in existing models, aligning simulated results with observed trends.

Findings

Mass-based selection doubles blue straggler count but correlates well with observational criteria.

Model blue stragglers show similar trends with cluster properties as real Milky Way blue stragglers.

Number of blue stragglers in the core weakly depends on the collisional parameter Gamma.

Abstract

We created artificial color-magnitude diagrams of Monte Carlo dynamical models of globular clusters, and then used observational methods to determine the number of blue stragglers in those clusters. We compared these blue stragglers to various cluster properties, mimicking work that has been done for blue stragglers in Milky Way globular clusters to determine the dominant formation mechanism(s) of this unusual stellar population. We find that a mass-based prescription for selecting blue stragglers will choose approximately twice as many blue stragglers than a selection criterion that was developed for observations of real clusters. However, the two numbers of blue stragglers are well-correlated, so either selection criterion can be used to characterize the blue straggler population of a cluster. We confirm previous results that the simplified prescription for the evolution of a collision or merger product in the BSE code overestimates their lifetimes. We show that our model blue stragglers follow similar trends with cluster properties (core mass, binary fraction, total mass, collision rate) as the true Milky Way blue stragglers, as long as we restrict ourselves to model clusters with an initial binary fraction higher than 5%. We also show that, in contrast to earlier work, the number of blue stragglers in the cluster core does have a weak dependence on the collisional parameter Gamma in both our models and in Milky Way globular clusters.