A global group has pioneered a “motion-picture” technique for measuring the precession charge of the Milky Way’s disk warp. Utilizing a pattern of Cepheid variable stars of various ages, this technique permits the precession course and charge of the Milky Way’s warp to be clearly noticed.
Based mostly on these measurements, the analysis group revealed that the present dark matter halo of the Milky Way is barely oblate. The ensuing paper, “A barely oblate dark matter halo revealed by a retrograde precessing galactic disk warp,” is published in Nature Astronomy.
Within the nearby universe, almost one-third of disk galaxies usually are not excellent disks however exhibit a warped form resembling a potato chip. Astronomers confer with this phenomenon as a disk warp. The Milky Way, as a typical disk galaxy, additionally has this warp characteristic.
This tilted, rotating galactic disk, very similar to a spinning prime, inevitably undergoes precession as a result of torque exerted by the encompassing dark matter halo. Nonetheless, the measurement of this essential dynamic parameter, each in course and charge, has been extremely debated.
It is because earlier measurements relied on oblique kinematic strategies, the place the tracers used are topic to dynamical perturbations or heating results, significantly limiting their accuracy and precision.
This examine used 2,600 classical Cepheid variable stars found by Gaia as tracers, together with exact distance and age knowledge from each Gaia and LAMOST. Utilizing this pattern, the researchers utilized the “motion-picture” technique to assemble the three-dimensional construction of the Milky Way’s disk throughout populations of varied ages.
By “seeing” how the disk warp evolves with age, this examine discovered that the warp precesses in a retrograde course at a charge of two km/s/kpc (or 0.12 levels per million years).
Additional detailed measurements present that the precession charge decreases with radial distance, indicating that the present dark matter halo enveloping the warp is barely oblate, with a flattening worth q between 0.84 and 0.96.
This measurement gives a vital anchor level for learning the evolution of the Milky Way’s dark matter halo.
Extra data:
Yang Huang et al, A barely oblate dark matter halo revealed by a retrograde precessing galactic disk warp, Nature Astronomy (2024). DOI: 10.1038/s41550-024-02309-5
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‘Movement-picture’ technique reveals form of the Milky Way’s dark matter halo (2024, July 1)
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