The Density Structure of Simulated Stellar Streams

• Published in: The Astrophysical journal Vol. 889; no. 2; pp. 107 - 118
• Main Author: Carlberg, Raymond G.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.02.2020; IOP Publishing
• Subjects: Astrophysics; body simulations; Circular orbits; Cold dark matter; Computer simulation; Correlation; Correlation analysis; Dark matter; Density; Galactic halos; Globular star clusters; Halos; Milky Way dark matter halo; Milky Way stellar halo; Model matching; N-body simulations; Noise levels; Orbits; Population (statistical); Star clusters; Stellar evolution; Tidal tails; Variation
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab61f0

Star particles in a set of dense clusters are self-consistently evolved within an LCDM dark matter distribution with an n-body code. The clusters are started on nearly circular orbits in the more massive sub-halos. Each cluster develops a stellar tidal stream, initially within its original sub-halo. When a sub-halo merges into the main halo the early time stream is dispersed as a somewhat chaotic thick stream, roughly the width of the orbit of the cluster in the sub-halo. Once the cluster orbits freely in the main halo the star stream forms a thin stream again, usually resulting in a thin stream surrounded by a wider distribution of star particles lost at earlier times. To examine the role of the lower-mass dark matter sub-halos in the creation of density variations along the thin tidal star streams two realizations of the simulation are run with and without a normal cold dark matter sub-halo population below 4 × 108 . About 70(40)% of thin streams show density variations that are 2(5) times the star count noise level, irrespective of the presence or absence of low-mass sub-halos. A counts-in-cells analysis (related to the two-point correlation function and power spectrum) of the density along nearly 8000° of streams in the two well matched models finds that the full sub-halo population leads to slightly larger, but statistically significant, density fluctuations on scales of 2°-6°.