Gaia Skymap

The images below show the skymap published by the Gaia Collaboration as part of their first data release [A.G.A. Brown et al., A&A 595 (2016) A2], and screenshots thereof. The Gaia skymap has two triangular features in the plane of the Milky Way at nearly symmetric locations with respect to the galactic center. The left triangle is in the direction of galactic coordinates (l,b) = (80°, 0°), whereas the right triangle is in the direction (l,b) = (-91°, 0°). The screenshots are close-ups of the two features. Locator figures are provided.

In arXiv:2007.10509, S. Chakrabarty, A. Gonzalez, Y. Han and P. Sikivie interpret the triangular features as the imprints of a caustic ring of dark matter upon baryonic matter in the galactic disk in the two directions tangent to the ring from our perspective. The left triangle coincides with a triangular feature seen previously in the IRAS skymap; see here . The IRAS skymap does not have a discernable feature coinciding with the Gaia right triangle.

The caustic ring allegedly responsible for the features lies very close to the galactic plane, tilted with respect to it to the right by approximately 0.66°. Assuming it is circular between the two tangent points, the caustic ring center lies in a direction 5.81° to the right of the galactic center. It is very likely that the Sun is located within the tricusp volume of the caustic ring. If so, there are four prominent flows on Earth associated with the caustic ring.

It is shown in the aforementioned work that dust is entrained by cold axion dark matter flows. The authors propose that the dust particles follow the same trajectories as the axions and thus form the same caustics. This accounts for the sharpness of the triangular features. In the left tangent direction, the caustic ring lies in the Orion Spur of the Sagittarius Spiral Arm. The dust particles are heated there by stellar activity and reradiate the heat in the infrared where IRAS is sensitive. In the right tangent direction, the caustic ring lies in a relatively quiet region. The dust particles are insufficiently heated there for their presence to be revealed in the IRAS map.