Clumpy Streams from Clumpy Halos: Detecting Missing Satellites with Cold Stellar Structures

Understand

Dynamically cold stellar streams are ideal probes of the gravitational field of the Milky Way.

• This paper re-examines the question of how such streams might be used to test for the presence of "missing satellites" -the many thousands of dark-matter subhalos with masses 10^5-10^7Msolar which are seen to orbit within Galactic-scale dark-matter halos in simulations of structure formation in LCDM cosmologies.
• Analytical estimates of the frequency and energy scales of stream encounters indicate that these missing satellites should have a negligible effect on hot debris structures, such as the tails from the Sagittarius dwarf galaxy.
• However, long cold streams, such as the structure known as GD-1 or those from the globular cluster Palomar 5 (Pal 5) are expected to suffer many tens of direct impacts from missing satellites during their lifetimes.