Constraining a Thin Dark Matter Disk with $Gaia$

If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy that is coplanar with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including periodic comet impacts. Using the first data release from the Gaia space observatory, we search for a dark disk via its effect on stellar kinematics in the Milky Way. Our new limits disfavor the presence of a thin dark matter disk, and we present updated measurements on the total matter density in the Solar neighborhood.

Figure 1

The measured number density profiles (top) and velocity distributions (bottom) for the tracer stars in our sample volume, subdivided by spectral type. The solid lines are the best fit from our analysis, assuming no DD.

Figure 2

The 95% constraint on the DD surface density ${\mathrm{\Sigma }}_{\mathrm{DD}}$ as a function of the scale height $h_{\mathrm{DD}}$, as found in this Letter and in Kramer and Randall [51]. The star indicates fiducial DD parameters that can account for phenomena such as periodic comet impacts [36]. Also shown is a comparison of the limit to the 68% and 95% containment regions (in dark and light green, respectively) on the expected limit from simulated data generated under the null hypothesis of no DD.