Kinematic origin of white dwarfs in the solar neighborhood

Abstract

Thanks to the recent space-borne mission Gaia, there is a nearly complete sample of white dwarfs up to about 100 parsecs from the Sun, which may have very diverse origins. We aim to compute the Galactic orbits for white dwarfs observed in our Solar neighborhood, in order to analyze the most probable regions of the Galaxy where they could have formed, the distribution of their orbital parameters, as well as the observational biases introduced when constructing the local sample. We used a detailed Galactic orbit integration package, in conjunction with a detailed population synthesis code specifically designed to replicate the different Galactic components of the white dwarf population. Synthetic stars are generated based on the current observational sample, and subsequently, their orbital integration allows for the reconstruction of the population past history. Our kinematic analysis reveals that the majority of thin disk, thick disk, and halo white dwarfs will have left our 100 pc neighborhood in approximately 3.30, 1.05, and 0.6 Myr, respectively. The spatial distribution of the integrated thin disk orbits suggests that 68 percent of these stars were formed at less than 1 kpc from the Sun, while most of thick disk members suffered from radial disk migration. The local halo white dwarfs typically belong to the "inner halo", being their orbits mostly planar and not extending beyond R = 20-25 kpc. Despite the observational bias, the distribution of orbital parameters is well represented by the observed sample. The Solar neighborhood is a transitory concept, which must be taken into account when analyzing the overall properties of such a population, such as its age distribution, metallicities or formation history. Even so, the kinematic properties observed by recent missions such as Gaia are representative of the total population up to a distance of approximately 500 pc [abridged].

Accepted for publication in A&A, 11 pages, 8 figures, 7 tables

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