Abstract
A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3{\pi} Steradian Survey Processing Version 2 to construct the White Dwarf Luminosity Functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalised maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833 sr, which is 83% of the 3{\pi} sky and 62% of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100.
Highlights
Main sequence (MS) stars with initial mass less than 8 M end up as white dwarfs (WDs) at the end of their lives
The derived star formation history (SFH) was mostly consistent with R13 but it lacks a peak at recent times which they claim as noise being amplified by the algorithm developed by R13
There are large correlated errors between parallax and proper motion when coverage in parallactic factor is low. These correlations are not propagated into the final catalogue products in Pan–STARRS 1 Surveys (PS1) PV2, so the proper motions from the 5-parameter solutions have increased scatter over those that can be computed from the 4-parameter solutions
Summary
Main sequence (MS) stars with initial mass less than 8 M end up as white dwarfs (WDs) at the end of their lives. Tremblay et al (2014) used a set of confirmed spectroscopic WDs with well determined distance, temperature and surface gravity, the mass and radius, to derive the age of each individual WD In their case, the derived SFH was mostly consistent with R13 but it lacks a peak at recent times which they claim as noise being amplified by the algorithm developed by R13. The sample is biased towards hot and warm WDs (typically Teff > 14, 000 K for DAs, Teff > 8, 000 K for DBs; and a minimum of Teff = 6, 000 K) These catalogues are of little use when it comes to the faint end of the WDLF which reveals the star formation scenario of the Galaxy at early times. The final section finishes with a summary and a brief discussion
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