The photometric evolution of dissolving star clusters: II. Realistic models. Colours and M/L ratios

Abstract

Evolutionary synthesis models are the prime method to construct models of stellar populations, and to derive physical parameters from observations. One of the assumptions for such models so far has been the time-independence of the stellar mass function. However, dynamical simulations of star clusters in tidal fields have shown the mass function to change due to the preferential removal of low-mass stars from clusters. Here we combine the results from dynamical simulations of star clusters in tidal fields with our evolutionary synthesis code GALEV to extend the models by a new dimension: the total cluster disruption time. We reanalyse the mass function evolution found in N-body simulations of star clusters in tidal fields, parametrise it as a function of age and total cluster disruption time and use this parametrisation to compute GALEV models as a function of age, metallicity and the total cluster disruption time. We study the impact of cluster dissolution on the colour (generally, they become redder) and magnitude (they become fainter) evolution of star clusters, their mass-to-light ratios (off by a factor of ~2 -- 4 from standard predictions), and quantify the effect on the cluster age determination from integrated photometry (in most cases, clusters appear to be older than they are, between 20 and 200%). By comparing our model results with observed M/L ratios for old compact objects in the mass range 10^4.5 -- 10^8 Msun, we find a strong discrepancy for objects more massive than 10^7 Msun (higher M/L). This could be either caused by differences in the underlying stellar mass function or be an indication for the presence of dark matter in these objects. Less massive objects are well represented by the models. The models for a range of total cluster disruption times are available online. (shortened)

MNRAS, in press, data are available at http://www.phys.uu.nl/~anders/data/SSP_varMF/, http://data.galev.org and soon also from CDS ... sorry for the sometimes strange layout, that's LaTeX

References in corpus (22)

• Scaled solar tracks and isochrones in a large region of the Z-Y plane I. From the ZAMS to the TP-AGB end for 0.15 - 2.5 Mo stars
• Gas expulsion and the destruction of massive young clusters
• The Initial-Final Mass Relation: Direct Constraints at the Low Mass End
• Star cluster disruption by giant molecular clouds
• Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters
• GALEV evolutionary synthesis models - I. Code, input physics and web-interface
• From star clusters to dwarf galaxies: The properties of dynamically hot stellar systems
• Lifetimes of tidally limited star clusters with different radii
• The Nature of UCDs: Internal Dynamics from an Expanded Sample and Homogeneous Database
• Evidence for primordial mass segregation in globular clusters
• The effect of spiral arm passages on the evolution of stellar clusters
• Bright globular clusters in NGC 5128: the missing link between young massive clusters and evolved massive objects
• Mass segregation in very young open clusters -- A case study of NGC 2244 and NGC 6530
• Intermediate Mass Black Hole Induced Quenching of Mass Segregation in Star Clusters
• An extreme IMF as an explanation for high M/L ratios in UCDs? The CO index as a tracer of bottom heavy IMFs
• Radio observations of NGC 2808 and other globular clusters: constraints on intermediate mass black holes
• The influence of gas expulsion and initial mass-segregation on the stellar mass-function of globular star clusters
• The photometric evolution of star clusters and the preferential loss of low-mass bodies - with an application to globular clusters
• The Main Sequence of Star Clusters
• The Young Cluster Population of M82 Region B
• Explaining the mass-to-light ratios of globular clusters
• Monte Carlo Simulations of Metal-Poor Star Clusters

Cited by in corpus (25)

• Fitting the integrated Spectral Energy Distributions of Galaxies
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• The devil is in the tails: the role of globular cluster mass evolution on stream properties
• The evolution of the stellar mass function in star clusters
• Understanding the Dynamical State of Globular Clusters: Core-Collapsed vs Non Core-Collapsed
• Direct N-body simulations of globular clusters: (I) Palomar 14
• The ACS Fornax Cluster Survey. IX. The Color-Magnitude Relation of Globular Cluster Systems
• Star Clusters in the Tidal Tails of Interacting Galaxies: Cluster Populations Across a Variety of Tail Environments
• N-body models of globular clusters: metallicity, half-light radii and mass-to-light ratios
• Dynamical masses and mass-to-light ratios of resolved massive star clusters -- II. Results for 26 star clusters in the Magellanic Clouds
• Formation of star clusters and enrichment by massive stars in simulations of low-metallicity galaxies with a fully sampled initial stellar mass function
• Evidence for Two Distinct Stellar Initial Mass Functions
• New insights into the star formation histories of candidate intermediate-age early-type galaxies from K'-band imaging of globular clusters
• Star cluster dynamics
• Evidence for Two Distinct Stellar Initial Mass Functions : Probing for Clues to the Dichotomy
• Stochastic stellar cluster IMFs: Models and impact on integrated cluster parameter determination
• The evolution of luminosity, colour and the mass-to-luminosity ratio of Galactic open clusters: comparison of discrete vs. continuous IMF models
• Evidence for Two Distinct Stellar Initial Mass Functions : Revisiting the Effects of Cluster Dynamical Evolution
• The colour-magnitude relation of Globular Clusters in Centaurus and Hydra - Constraints on star cluster self-enrichment with a link to massive Milky Way GCs
• Globular clusters as probes of dark matter cusp-core transformations
• Under Pressure: Star Clusters and the Neutral Hydrogen Medium of Tidal Tails
• The Ophiuchus stream progenitor: a new type of globular cluster and its possible Sagittarius connection
• Effect of dynamical interactions on integrated properties of globular clusters
• Wide HI profile galaxies