A Monte Carlo analysis of the velocity dispersion of the globular cluster Palomar 14

TL;DR

This study uses Monte Carlo simulations and high-resolution spectroscopy to analyze the velocity dispersion of globular cluster Palomar 14, testing Newtonian and alternative gravity models against observational data.

Contribution

It provides a comprehensive comparison of dynamical models with observations, confirming Newtonian models with low binary fractions and standard M/L ratios fit the data well.

Findings

Newtonian models with f_b<30% match observations

Models with high binary fractions overestimate velocity dispersion

Modified Newtonian Dynamics models require lower M/L ratios to fit data

Abstract

We present the results of a detailed analysis of the projected velocity dispersion of the globular cluster Palomar 14 performed using recent high-resolution spectroscopic data and extensive Monte Carlo simulations. The comparison between the data and a set of dynamical models (differing in fraction of binaries, degree of anisotropy, mass-to-light ratio M/L, cluster orbit and theory of gravity) shows that the observed velocity dispersion of this stellar system is well reproduced by Newtonian models with a fraction of binaries f_b<30% and a M/L compatible with the predictions of stellar evolution models. Instead, models computed with a large fraction of binaries systematically overestimate the cluster velocity dispersion. We also show that, across the parameter space sampled by our simulations, models based on the Modified Newtonian Dynamics theory can be reconciled with observations only assuming values of M/L lower than those predicted by stellar evolution models under standard assumptions.