Space Distribution, Motional Orbits And Monte Carlo Simulation Of Globular Clusters In The Galaxy

Globular clusters are the oldest known objects in the Milky Way. The research of globular clusters has important significance for the study of structure and evolution of the galaxies.The 29 F globular clusters in the galaxy are selected as samples in my paper (The space distribution and motional orbits of the samples have not been researched in detail before.) .According to the basic parameters: azimuth coordinates, distances from the sun, radial velocities and proper motions of sample clusters, the initial positions and velocities of the samples are reduced using the galactic coordinates, and their orbits are integrated by numerical method for three different galactic gravitational potential models. Finally the initial observational data are produced by Monte Carlo method, and the orbital parameters are calculated using the simulation data for the three sample clusters. The relationship between the distribution morphologies of the orbital parameters and the initial observational date as well as the different galactic gravitational potential models are discussed.The calculating results show:(1) Most of samples are located in 5 kpc -10 kpc from Galactic center. All of the sample clusters present a spherical symmetrical distribution around the Galactic center, and their space velocities are presented a ellipsoidal distribution;(2) According to the metallicity and basic characters, the sample clusters are separated into HB subgroup and MP subgroup. The number of samples are changed with metallicity [Fe/H], and there is a peak at [Fe/H] = - 1.6;(3) The orbits of sample clusters show mostly limited, periodic characteristics, but the orbits are not closed completely, their maximal galactocentric distance is less than 40 kpc. The differences in orbital morphologies due to different potentials is slighting, however, given a certain potential, for clusters that have perigalactic distance smaller than 1 kpc, some orbits may exhibit a chaotic behavior. The correlation between the metallicity of samples and the orbital morphologies is unclearly;(4) It is found that the semi-major axis, apogalactic distance and azimuth period of 29 sample clusters are changed with their metallicity similarly,but a obvious correlation is seen between orbital eccentricity and metallicity. There is a fraction of 24% of the sample clusters with eccentricities lower than 0.4. The different Galactic gravitational potential have not clear influence upon the perigalactic distance, eccentricity and uncertainty of orbital parameters, but which is significant for other parameters, such as the apogalactic distance, semi-major axis, radial period and azimuth period and so on;(5) The Monte Carlo simulation show that: The distribution morphologies of the orbital parameters which are produced by simulation data are separated into three types: Gaussian profile, semi-Gaussian profile and non-Gaussian profile. The influence of observational data on the orbital parameters is related to the selected of sample clusters and the types of the orbital parameters. Besides, considering the differences of the galactic gravitational potential models, there is different influence for the distribution morphologies of all of the orbital parameters of the selected sample clusters .