Weighing the Galactic disk using phase-space spirals II. Most stringent constraints to a thin dark disk using Gaia EDR3

Abstract

Using the method that was developed in the first paper of this series, we measure the vertical gravitational potential of the Galactic disk from the time-varying structure of the phase-space spiral, using data from Gaia as well as supplementary radial velocity information from legacy spectroscopic surveys. For eleven independent data samples, we inferred gravitational potentials that were in good agreement, despite the data samples' varied and substantial selection effects. Using a model for the baryonic matter densities, we inferred a local halo dark matter density of 0.0085 ± 0.0039 M pc −3 = 0.32 ± 0.15 GeV cm −3 . We were also able to place the most stringent constraint to the surface density of a thin dark disk with a scale height ≤ 50 pc: an upper 95 % confidence limit of roughly 5 M pc −2 (compared to previous limit of roughly 10 M pc −2 , given the same scale height). For the inferred halo dark matter density and thin dark disk surface density, the uncertainties are dominated by the baryonic model. With this level of precision, our method is highly competitive with traditional methods that rely on the assumption of a steady state. In a general sense, this illustrates that time-varying dynamical structures are not solely obstacles to dynamical mass measurements, but can also be regarded as assets containing useful information.

Galactic Geology: Probing Time-Varying Dark Matter Signals with Paleo-Detectors

“…Existing constraints on a dark disk arise from the kinematics of stars in the MW [68][69][70][71][72][73][74]. However, these constraints arise from gravitational interactions and are thus insensitive to the scattering cross section of the DM comprising the dark disk.…”

“…1. Astrometric measurements of stars are sensitive to the gravitational effects of a dark disk and provide upper limits on its surface density, Σ disk 5 M /pc 2 [68][69][70][71][72], although they are subject to a host of uncertainties [73,74]. We will show that, depending on the scattering cross section of the DM making up the dark disk, one could 0 20 40 We choose illustrative values for the various signal parameters (described in Sec.…”

Estimating the local dark matter density in a non-axisymmetric wobbling disc

“…In the case of Sivertsson et al (2018), these are 'α-old' stars that are kinematically hotter; for Salomon et al (2020), these are stars in the Northern Hemisphere that show more prominent signs of disequilibrium than those in the Southern Hemisphere. Finally, the purple datapoint shows a recent determination from Widmark et al (2021) that is distinct from the other local methods in that it harnesses the fact that the Milky Way disc is wobbling and ringing. (Data taken from Xia et al (2016); Sivertsson et al (2018); Buch et al (2019); Guo et al (2020); Salomon et al (2020); Widmark et al (2021).).…”

“…Finally, the purple datapoint shows a recent determination from Widmark et al (2021) that is distinct from the other local methods in that it harnesses the fact that the Milky Way disc is wobbling and ringing. (Data taken from Xia et al (2016); Sivertsson et al (2018); Buch et al (2019); Guo et al (2020); Salomon et al (2020); Widmark et al (2021).). Schutz et al 2018;Buch et al 2019;Widmark 2019).…”

“…More recently, newer methods have been introduced, like 'made to measure ' (e.g. Syer & Tremaine 1996;Bovy et al 2018), and a recent attempt to harness the Milky Way disc's disequilibrium to estimate ρDM, (Widmark et al 2021). Some studies exploit the vertical kinematics of stars up to a height z ∼ 1 − 3 kpc above the Galactic disc (e.g.…”