Light Element Abundances and Multiple Populations in M10

TL;DR

This study analyzes multiple stellar populations in the globular cluster M10 using CN and CH spectral measurements, revealing a majority of CN-enhanced stars, similar radial distributions among populations, and insights into stellar evolution and classification methods.

Contribution

It provides the first detailed analysis of CN and CH band data for M10, confirming the fraction of second-generation stars and comparing multiple classification techniques.

Findings

60% of stars are CN-enhanced or second-generation.

Radial distributions of populations are similar, indicating dynamical evolution.

CN and other classification methods agree on population fractions.

Abstract

We present CN and CH band measurements for 137 RGB and AGB stars in the Galactic globular cluster M10. Our measurements come from low resolution spectroscopy taken with the Hydra spectrograph on the WIYN-3.5m telescope. We use these measurements to identify two populations of stars within the cluster, a CN-normal and CN-enhanced, and find that in our sample 60% of stars are CN-enhanced. Our large sample allows us to conduct a detailed analysis on the carbon and nitrogen abundances and the radial distribution of each population separately. Our analysis of the radial dependence shows that each population has the same radial distribution in the cluster, which is likely due to the cluster being dynamically evolved. We also compare our results to other methods of classifying multiple populations in globular clusters such as the Na-O anti-correlation and the HST pseudo-color magnitude diagrams. We find that these three methods of identifying multiple populations are in good agreement with each other for M10 and all lead to an estimate of the fraction of second generation stars approximately equal to 60%. Among AGB stars, when classified by the CN band, there appears to be a lack of second generation stars when compared to the RGB stars. However, when classified by [N/Fe], we find a similar 60% of AGB stars in the second generation. Finally, we use the measured carbon and nitrogen abundances in RGB stars to study the change of each element with magnitude as stars evolve up the RGB, comparing the results to globular clusters of similar metallicity, M3 and M13.