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Published September 11, 2022 | Version v1
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The velocity distribution of white dwarfs in Gaia EDR3

  • 1. Department of Astronomy and Theoretical Physics, Lund University, Sweden

Description

There are ~1.5 billion sources with parallaxes and proper motions in Gaia EDR3. When investigating velocity distributions of stars, one typically combines this with radial velocity measurements to give a full 3D velocity. As Gaia currently has ~7.2 million sources with radial velocities, this leaves only ~0.5% of sources which one can typically use. The wealth of information locked within the remaining ~99.5% cannot be overstated. 
However, with a distribution of stars widely spread across the sky we can statistically estimate its velocity distribution using a maximum likelihood approach and just the parallaxes and proper motions. By removing the need for radial velocities, we can can investigate the kinematics of different populations previously unavailable for such studies. One such population are white dwarfs and in this work, we use a large sample of ~130 000 white dwarfs in Gaia EDR3 and find the velocity distribution and dynamics of several sub-samples within different brightness and colour cuts.
The velocity distribution of nearby white dwarfs has never been determined using such a large sample. We may learn more about the Solar neighbourhood from how this distribution differs from that of main sequence stars. Interestingly the Colour-Magnitude diagram of white dwarfs from Gaia DR2 revealed a bifurcation, the cause of which is an active topic of research. The second sequence is attributed to a mix of high-mass H-dominated and lower-mass He-dominated WDs. Higher mass WDs will have lived shorter lives and show less dynamical heating than their low-mass counterparts and so can be distinguished through their kinematics. In our work, we investigate these kinematics and velocity distribution of the WDs as a whole as well as in the two separate sequences to provide further insight into these populations.

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