Light Element Inhomogeneities and Multiple Populations in Galactic Globular Clusters
Abstract
Spectroscopic and photometric observations have shown that globular clusters are complex systems hosting multiple stellar populations showing variations in light elements such as C, N, O, and Na. However, while multiple populations have been found in every Galactic globular cluster studied, their formation is still not well understood. We present results from a project designed to increase the number of observational constraints on current formation theories and to better understand the chemical nature of multiple populations. We have obtained low-resolution spectra for 100-140 stars ranging in magnitude from the tip of the RGB down to the main sequence turn-off in each of three globular clusters covering a range in metallicity from [Fe/H] = -2.10 to -0.78: M53, M10, and M71. Our observations come from the multi-object spectrograph, Hydra, on the WIYN-3.5m telescope. We measure the blue CN and CH bands around 3883 and 4300 angstroms, respectively, which allows us to derive C and N abundances, and determine populations based on both CN band strength and N abundance. The population determinations allow us to study the ratio of stars in each population, which can be used to constrain formation scenarios, and to make comparisons with other methods of classifying multiple populations such as those using the Na-O anti-correlation and HST UV photometry. Another necessary constraint for any formation theory of multiple populations is the radial distribution of each population, and the extended radial coverage of our samples allows us to determine the radial distribution for each cluster studied. Finally, with C and N abundances for stars over much of the giant branch in the two lower metallicity clusters, we study and contrast the evolutionary effects on the surface abundances of these elements in each population.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23334205G