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gaia data release 3 documentation

14.3 Comparison to models

14.3.5 Radial velocities

The median of the radial velocity is computed in each HEALPix pixel and shown shown in Figure 14.46 for the magnitude range 12<G<13. We see that there is no systematic significant difference between model and data, at least not that can be attributed to the data themselves.

Figure 14.46: Median of radial velocities computed in HEALPix pixels, in km⁢s-1, in Gaia DR3 (left), in GOG20 (middle) and their differences (right), in the magnitude range 12<G<13.

Figure 14.47 shows the radial velocity averaged over the whole sky per magnitude bin, for Gaia DR3, Gaia DR2, and GOG20. From G = 4 to 15, the Gaia DR3 values are in agreement with GOG20 at the level of 1.5 km⁢s-1 or less. We note that it was at the level of 1 km⁢s-1 or less with Gaia DR2. The dependency on the G magnitude seen in the data is not predicted by the model and could indicate some systematics that are not understood yet.

Figure 14.47: Median of radial velocities in km⁢s-1 over the whole sky as a function of magnitude in Gaia DR3 (blue) and Gaia DR2 (pink), compared to GOG20 (green).

Summary of the results:

  • •

    Data and model distributions are in overall agreement to G = 15, one magnitude fainter than in Gaia DR2, at the level of 1.5 km⁢s-1.

  • •

    The dependency on the median of radial velocities over the whole sky versus G magnitude, not predicted by the model, could indicate some systematics that are not understood yet.