Binaries and the Dynamical Evolution of Globular Clusters.

Globular Cluster;Binary;Binary Fraction;Dynamical Evolution;Mass Segregation;Stellar System;Astronomy;Science;Astronomy and Astrophysics

Ji, JunMonnier, John D. ;

University of Michigan

关键词: Globular Cluster;    Binary;    Binary Fraction;    Dynamical Evolution;    Mass Segregation;    Stellar System;    Astronomy;    Science;    Astronomy and Astrophysics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/89628/jijun_2.pdf?sequence=3&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Binaries are thought to be the primary heating source in globular clusters, since they can heat the environment of globular clusters by converting their binding energy to the kinetic energy of the incoming stars through the dynamical interactions. Even a small primordial binary fraction is sufficient to postpone globular clusters from the core collapse for many relaxation times. So the binary fraction is an essential parameter which can dramatically affect the dynamical evolution of globular clusters. In this thesis work, I determined the binary fractions for a sample of 35 Galactic globular clusters with their color-magnitude diagrams (CMDs), which covers a wide range of the dynamical ages and metallicity. Those CMDs were constructed with the PSF photometry by Dolphot (V1.2) from their HST ACS archival data. Three different methods were used to estimate the binary fractions within the core, the half-mass radius, and the whole field of view regions. The binary fractions along the cluster radial bins were also analyzed. From the results, I found that the mean binary fractions within the core and the half-mass radii are 7.0% and 5.6%, respectively. The binary fractions within the core and the half-mass radii correlate with the cluster ages, with decreasing binary fractions against time, but not with their dynamical times and metallicity. The binary fractions within the half-mass radius also correlate with the cluster absolute V magnitudes, with fainter clusters having higher binary fractions. The radial distribution of the binary fractions show a significant correlation with the cluster radii, with decreasing values outwards. This is consistent with the mass segregation effect predicted by the simulations of the dynamical evolution of globular clusters. I also compiled a catalog containing 6,004 high mass-ratio binary candidates selected from 23 Galactic globular clusters in our sample through their CMDs, which can be used to search the main-sequence-main-sequence binaries in globular clusters with the future radial velocity observations.