Sirui Wu

A stellar stream’s curvature traces the pull of its host’s dark matter halo.

A stellar stream’s curvature traces the pull of its host’s dark matter halo. Applied to 15 streams from the Stellar Stream Legacy Survey, Potamides constrains each halo’s projected flattening and orientation. Streams with edge-on loops or sharp turns constrain it most, great-circle-like ones barely at all, and three hint that the stellar disk shapes the inner gravitational field. Led by Sirui Wu.

Potamides is a JAX package that infers a galaxy’s mass distribution from the shapes of its stellar streams.

Potamides is a JAX package that infers a galaxy’s mass distribution from the shapes of its stellar streams. Instead of simulating a stream for every trial potential, it fits the observed track with splines and compares its curvature directly to the potential’s accelerations, covering the pipeline from annotating streams to evaluating likelihoods. Led by Sirui Wu.

Cold dark matter predicts triaxial halos; self-interacting dark matter rounds them toward spheres.

Cold dark matter predicts triaxial halos; self-interacting dark matter rounds them toward spheres. A stellar stream in a spherical halo can never curve away from its host galaxy’s center in projection, but one in a triaxial halo can. The rate of these convexities tracks halo shape across a population, so catalogs on the scale of Euclid, Rubin and Roman can tell CDM from SIDM at up to 5σ.

Euclid is turning up stellar streams around galaxies across a cosmological volume.

Euclid is turning up stellar streams around galaxies across a cosmological volume. A stream’s shape on the sky constrains the shape and center of its host’s dark matter halo, complementing weak lensing. Across 13 galaxies in Euclid’s first quick data release, halos are consistent with spherical, albeit with a mild preference for flattening, q = 0.95 (+0.05, −0.10), in line with ΛCDM. Thousands more streams are expected over the mission.

co-lead developer

Constrain gravitational potentials from stellar stream curvature

A JAX package that fits stream tracks with splines and compares their curvature directly to a potential's accelerations. Co-led with Sirui Wu.