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Age of the Cluster

A purely qualitative way to determine the age of the cluster would be to compare the cluster luminosity function of our cluster with that of a model luminosity function (Lada & Lada 1995). Comparing our apparent K-magnitude cluster luminosity function with the continuous star formation model luminosity function we find that our cluster is about $5 \times 10^{6}$ years old by comparing the drop-off rate and the limiting highest magnitude with that of the model function. This matches closely with previous estimates for the age of the clusters (Lada & Lada 1995).

A more quantitative way to determine the age of the cluster would be to calculate the absolute magnitudes of the stars in our cluster by using Equation 4 assuming the extinction that we determined in Section 5.2. The brightest stars in our cluster can help us determine the age of the cluster because the most massive stars will evolve off of the main sequence the fastest since they have the shortest lifetime. Thus, if we examine which of the most massive stars are missing from the cluster, we can determine a lower limit for the age of our cluster since we know that the age of the cluster has to be at least as old as the lifetime of the most recent massive star that had evolved off the main sequence from the cluster. However, when we did these calculations, we found that the age of our cluster was much higher than previous estimates. This is probably due to the standards of our data as we optimized our data acquisition methods to obtain stars of lowest magnitudes by taking a high integrated exposure time, which saturated some of the brightest stars in our cluster. If the fall skies were clear for more nights, we could have gone back to obtain better data for bright stars so we could use this method, but we will leave this as a future exercise.


next up previous
Next: Mass of Dimmest Stars Up: Cluster Luminosity Function Previous: Cluster Luminosity Function
Joey Cheung 2006-11-15