Explaining the color distributions of globular cluster systems in elliptical galaxies.
The colors of globular clusters in most large elliptical galaxies are bimodal. This is generally taken as evidence for the presence of two cluster subpopulations that have different geneses. However, here we find that, because of the nonlinear nature of the metallicity-to-color transformation, a coeval group of old clusters with a unimodal metallicity spread can exhibit color bimodality. The models of cluster colors indicate that horizontal-branch stars are the main drivers behind the empirical nonlinearity. We show that the scenario gives simple and cohesive explanations for all the key observations and could simplify theories of elliptical galaxy formation.
Yoon
Suk-Jin
SJ
Department of Astronomy and Center for Space Astrophysics, Yonsei University, Seoul 120-749, Korea. sjyoon@galaxy.yonsei.ac.kr
Yi
Sukyoung Ken
SK
Lee
Young-Wook
YW