The binary fractions in the massive young Large Magellanic Cloud star clusters NGC 1805 and NGC 1818
Using high-resolution data sets obtained with the Hubble Space Telescope, we investigate the radial distributions of the F-type main-sequence binary fractions in the massive young Large Magellanic Cloud star clusters NGC 1805 and NGC 1818.We apply both an isochrone-fitting approach and x2 minimization using Monte Carlo simulations, for different mass-ratio cut-offs, q, and present a detailed comparison of the methods performance.Both methods yield the same radial binary fraction profile for the same cluster, which therefore supports the robustness and applicability of either method to young star clusters which are as yet unaffected by the presence of multiple stellar populations.The binary fractions in these two clusters are characterized by opposite trends in their radial profiles.NGC 1805 exhibits a decreasing trend with increasing radius in the central region, followed by a slow increase to the fields binary-fraction level, while NGC 1818 shows a monotonically increasing trend.This may indicate dominance of a more complicated physical mechanism in the clusters central region than expected a priori.Time-scale arguments imply that early dynamical mass segregation should be very efficient and, hence, likely dominates the dynamical processes in the core of NGC 1805.Meanwhile, in NGC 1818 the behaviour in the core is probably dominated by disruption of soft binary systems.We speculate that this may be owing to the higher velocity dispersion in the NGC 1818 core, which creates an environment in which the efficiency of binary disruption is high compared with that in the NGC 1805 core.
binaries close-binaries general-Magellanic Clouds-galaxies star clusters general-galaxies individual NGC 1805-galaxies NGC 1818
Chengyuan Li Richard de Grijs Licai Deng
Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian Distric Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian Distric Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Scienc
国际会议
昆明
英文
369-384
2014-05-01（万方平台首次上网日期，不代表论文的发表时间）