Investigating a possible dearth of stars with zero angular momentum in the solar neighbourhood.

Sammanfattning: Background. Carlberg & Innanen (1987) first proposed the idea of measuring the solar re- flex velocity (the velocity of the Sun around the galactic centre), Vg,⊙, using the momenta of the stars in the solar neighbourhood. The proposal was a consequence of the work of L. Martinet (Martinet 1974), where he proved that there should be a dearth of stars with zero angular momenta in the solar neighbourhood. The dip, corresponding to the dearth would then be centred around Vg,⊙. Hunt et al. (2016) pursued the idea further using data from the Gaia DR1, RAVE DR5, TGAS catalogues. While their results were encouraging, they were limited by the number of reliable stars that could be used in their model. Aim. Using the additional data from the Gaia DR3 catalogue, the aim of this report is to measure Vg,⊙ using the idea outlined above. Results. We start by considering different subsets of our data based on the position of the star relative to the Sun. We use an analytic Lorentzian dip profile to apply to these subsets of data. The parameters are estimated using MCMC. While some results from this analysis do find a dip, they are very sensitive to the subset of data on which the profile is applied. As an alternative, we simulate the orbits of several stars and use the fraction of time they spend near the galactic plane as a proxy model for the dip. The dip profiles generated from these simulations suggest that a dearth of stars should be present. Upon application to the sub-datasets, the results are found to be sensitive to the particular set. We summarise our findings and suggest some ideas that could be pursued to investigate this method hypothesis in the future.