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Mass modelling globular clusters in the Gaia era: a method comparison using mock data from an N-body simulation of M 4

Henault-Brunet, V, Gieles, Mark, Sollima, A, Watkins, LL, Zocchi, A, Claydon, Ian, Pancino, E and Baumgardt, H (2018) Mass modelling globular clusters in the Gaia era: a method comparison using mock data from an N-body simulation of M 4 Monthly Notices of the Royal Astronomical Society.

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Abstract

As we enter a golden age for studies of internal kinematics and dynamics of Galactic globular clusters (GCs), it is timely to assess the performance of modelling techniques in recovering the mass, mass profile, and other dynamical properties of GCs. Here, we compare different mass-modelling techniques (distribution-function (DF)-based models, Jeans models, and a grid of N-body models) by applying them to mock observations from a star-by-star N-body simulation of the GCM4 by Heggie. The mocks mimic existing and anticipated data for GCs: surface brightness or number density profiles, local stellar mass functions, line-of-sight velocities, and Hubble Space Telescope- and Gaia-like proper motions. We discuss the successes and limitations of the methods. We find that multimass DF-based models, Jeans, and N-body models provide more accurate mass profiles compared to single-mass DF-based models. We highlight complications in fitting the kinematics in the outskirts due to energetically unbound stars associated with the cluster (“potential escapers”, not captured by truncated DF models nor by N-body models of clusters in isolation), which can be avoided with DF-based models including potential escapers, or with Jeans models. We discuss ways to account for mass segregation. For example, three-component DF-based models with freedom in their mass function are a simple alternative to avoid the biases of single-mass models (which systematically underestimate the total mass, half-mass radius, and central density), while more realistic multimass DF-based models with freedom in the remnant content represent a promising avenue to infer the total mass and the mass function of remnants.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Henault-Brunet, V
Gieles, Markm.gieles@surrey.ac.uk
Sollima, A
Watkins, LL
Zocchi, A
Claydon, Iani.claydon@surrey.ac.uk
Pancino, E
Baumgardt, H
Date : 2018
Copyright Disclaimer : Copyright 2018 Oxford University Press. This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record will be available online at: https://academic.oup.com/mnras
Uncontrolled Keywords : galaxies: star clusters – globular clusters: general – stars: kinematics and dynamics
Depositing User : Melanie Hughes
Date Deposited : 27 Nov 2018 14:55
Last Modified : 27 Nov 2018 14:55
URI: http://epubs.surrey.ac.uk/id/eprint/849943

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