AR 16639 (Archival Research)

Mon Jul 15 06:26:07 GMT 2024

Principal Investigator: Matthew Walker
PI Institution: Carnegie Mellon University
Investigators (xml)

Title: Wide Binary Stars in Nearby Dwarf Galaxies: A Novel Probe of Dark Matter on Subgalactic Scales
Cycle: 29

The survival of widely separated binary stars within dense, low-mass dwarf galaxies depends strongly on the nature of dark matter. The standard Cold Dark Matter (CDM) model generically predicts that dwarf galaxy dark matter halos are composed of a smooth component with a centrally-divergent density "cusp", plus multitudes of self-bound subhalos, sub-subhalos, etc., down to a mass limit set by particle physics. Both smooth and clumpy components would disrupt wide binary stars, via tidal forces and perturbative encounters, respectively, leaving an imprint on the binary separation function. We propose to apply a novel, likelihood-based analysis to detect and characterize wide binary stars (separation > 3000 A.U.) in the nearby dwarf spheroidal galaxy Ursa Minor, which was observed for this purpose in Cycle 21 (GO-13470). We will apply Bayesian techniques to detect binary stars in a probabilistic sense. Improving on standard methodology that models the two-point correlation function, we will infer the binary separation function directly from the full distribution of stellar positions and known sensitivity function. We will interpret the results in the context of wide binary formation and survival in a dense dark matter halo environment, thereby providing novel tests of star formation in extreme environments and--especially if wide binaries are detected--a potentially definitive test of the CDM paradigm.