AR 2352 (Archival Research)

Fri Jun 2 18:12:22 GMT 2023

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: 1

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 "ultrafaint" 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 disrupt wide binary stars, via tidal forces and perturbative encounters, respectively, leaving an imprint on the binary separation function. We propose to exploit JWST's unprecedented sensitivy to perform a search for wide binary stars (separation > 1000 A.U.) in the nearby ultrafaint dwarf galaxy Draco II, which offers favorable conditions for a search and will be observed as part of Early Release Science program 1334. We will apply Bayesian techniques to detect binary stars as closely separated pairs, and to infer the binary separation function directly from the distribution of stellar positions. 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.