溶解星团的光度演化：II。逼真的模型。颜色和M/L比率
The photometric evolution of dissolving star clusters: II. Realistic models. Colours and M/L ratios
摘要：
演化综合模型是构造恒星星族模型和从观测数据中获取物理参数的主要方法。到目前为止，这种模型的假设之一是恒星质量函数的时间独立性。然而，在潮汐场中星团的动力学模拟表明，由于低质量恒星从星团中优先移除，质量函数会发生变化。在这里，我们结合我们的进化合成代码GALEV的星团在潮汐场的动力学模拟的结果扩展模型的一个新的维度：总集群中断时间。我们重新分析的质量函数的演化发现在N-体模拟的星团在潮汐场，parametrise它作为年龄和总集群中断时间的函数，并使用此parametrisation计算GALEV模型作为年龄，金属丰度和总集群中断时间的函数。我们研究了团簇溶解对颜色的影响（一般来说，它们会变得更红）和星等（它们会变得更暗），它们的质光比（与标准预测相差约2 - 4倍），并从综合测光中量化对星团年龄测定的影响（在大多数情况下，星团看起来比实际年龄老，在20 - 200%之间）。通过将我们的模型结果与观测到的质量范围在10^4.5 - 10^8 Msun之间的古老致密天体的M/L比进行比较，我们发现对于质量大于10^7 Msun（更高的M/L）的天体存在很大的差异。这可能是由基础恒星质量函数的差异引起的，也可能是这些物体中存在暗物质的指示。模型很好地代表了质量较小的物体。一系列集群总中断时间的模型可在线获得。（缩短）
英文摘要：
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)
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