http://arxiv.org/abs/1610.04743
The early accretion onto the Milky Way of satellite galaxies containing dense star clusters is a likely source of the halo globular clusters and the beginning of their associated stellar streams. The process of infall of a satellite with dynamical friction and subsequent merging is simulated with a simple evolving potential model. King model clusters are initiated within the satellite galaxy on circular orbits in a disk. Merging places the clusters on new orbits that substantially underfill their tidal radii, requiring that some internal relaxation of the clusters must be included to cause them to expand to their new tidal surface and start or continue to produce star streams. A toy model with a simplified Monte Carlo relaxation procedure gives the clusters star particles random velocity kicks at approximately the rate expected from collisional dynamics. The clusters expand and lose stars to evaporation leading to tidal streams that have local properties, including sub-halo gaps, as expected in a static halo. The main difference is that the streams are, on the average, denser and lower velocity dispersion near to the clusters than they are further away, making the older parts of the streams relatively less visible. Comparing the numbers of dense stellar systems that likely formed and orbit within the range of galactic radii where streams are visible to the Pan-STARRS1 survey finds that the number of detected streams is comparable to the number of “lost” globular clusters above $10^5$ M_sun, assuming that the detected streams follow the expectation that they arose from the most massive evaporated and evaporating clusters.
R. Carlberg
Tue, 18 Oct 16
61/70
Comments: N/A
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