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arXiv · 0909.2575

The mass-to-light ratio of rich star clusters

Christian M. Boily·Jean-Julien Fleck·Ariane Lançon·Florent Renaud
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Abstract

We point out a strong time-evolution of the mass-to-light conversion factor eta commonly used to estimate masses of unresolved star clusters from observed cluster spectro-photometric measures. We present a series of gas-dynamical models coupled with the Cambridge stellar evolution tracks to compute line-of-sight velocity dispersions and half-light radii weighted by the luminosity. We explore a range of initial conditions, varying in turn the cluster mass and/or density, and the stellar population's IMF. We find that eta, and hence the estimated cluster mass, may increase by factors as large as 3 over time-scales of 50 million years. We apply these results to an hypothetic cluster mass distribution function (d.f.) and show that the d.f. shape may be strongly affected at the low-mass end by this effect. Fitting truncated isothermal (Michie-King) models to the projected light profile leads to over-estimates of the concentration parameter c of delta c ~ 0.3 compared to the same functional fit applied to the projected mass density.

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Christian M. Boily, Jean-Julien Fleck, Ariane Lançon, Florent Renaud. 2009-09-14. The mass-to-light ratio of rich star clusters. https://doi.org/10.1007/s10509-009-0118-3

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