A critical look at the merger scenario to explain multiple populations and rotation in iron-complex globular clusters

作者：Gavagnin Elena^*; Mapelli Michela; Lake George

来源：Monthly Notices of the Royal Astronomical Society, 2016, 461(2): 1276-1287.

DOI：10.1093/mnras/stw1397

• methods: numerical
• stars: kinematics and dynamics
• globular clusters: general
• galaxies: star clusters: general

Merging has been proposed to explain multiple populations in globular clusters (GCs) where there is a spread in iron abundance (hereafter, iron-complex GCs). By means of N-body simulations, we investigate if merging is consistent with the observations of subpopulations and rotation in iron-complex GCs. The key parameters are the initial mass and density ratios of the progenitors. When densities are similar, the more massive progenitor dominates the central part of the merger remnant and the less massive progenitor forms an extended rotating population. The low-mass progenitor can become the majority population in the central regions of themerger remnant only if its initial density is higher by roughly the mass ratio. Tomatch the radial distribution of multiple populations in two iron-complex GCs (omega Cen and NGC 1851), the less massive progenitor needs to be four times as dense as the larger one. Our merger remnants show solid-body rotation in the inner parts, becoming differential in the outer parts. Rotation velocity V and ellipticity epsilon are in agreement with models for oblate rotators with isotropic dispersion. We discuss several kinematic signatures of a merger with a denser lower mass progenitor that can be tested with future observations.

• 出版日期2016-9-11