SCYON Abstract

Received on September 7 2006

Monte Carlo Simulations of Metal-Poor Star Clusters

AuthorsMartina Fagiolini (1, 2), Gabriella Raimondo (3), Scilla Degl'Innocenti (1,2)
Affiliation
(1) Dipartimento di Fisica, Universita di Pisa, Largo B. Pontecorvo 3, I-56126 Pisa, Italy
(2) INFN, Sezione di Pisa, Largo B. Pontecorvo 3, I-56126 Pisa, Italy
(3) INAF, Osservatorio Astronomico di Teramo, Via M. Maggini, I-64100, Teramo, Italy
Accepted byAstronomy & Astrophysics
Contactraimondo@oa-teramo.inaf.it
URLhttp://www.arxiv.org/abs/astro-ph/0609162
Links

Abstract

Metal-poor globular clusters (GCs) can provide a probe of the earliest epoch of star formation in the Universe, being the oldest stellar systems observable. In addition, young and intermediate-age low-metallicity GCs are present in external galaxies. Nevertheless, inferring their evolutionary status by using integrated properties may suffer from large intrinsic uncertainty caused by the discrete nature of stars in stellar systems, especially in the case of faint objects. In this paper, we evaluate the intrinsic uncertainty (due to statistical effects) affecting the integrated colours and mass-to-light ratios as a function of the cluster integrated visual magnitude (MVtot), which represents a quantity directly measured. Our approach is based on Monte Carlo techniques for randomly generating stars distributed according to the cluster's mass function. Integrated colours and mass-to-light ratios in different photometric bands are checked to be in good agreement with the observational values of low-metallicity Galactic clusters. We present integrated colours and mass-to-light ratios as a function of age for different assumptions on the cluster total V magnitude. We find that the intrinsic uncertainty cannot be neglected. In particular, in models with MVtot = -4 the broad-band colours show an intrinsic uncertainty so high as to prevent precise age evaluation of the cluster. Finally, the present predictions are compared with recent results available in the literature, showing in some cases non-negligible differences.