A photometric selection of White Dwarf candidates in SDSS DR10

TL;DR

This paper introduces a photometric method to select white dwarf candidates in SDSS data by calculating a probability score, enabling identification without spectroscopy and revealing many previously unconfirmed white dwarfs.

Contribution

The authors develop a novel probabilistic selection method based on colour and proper motion, applicable to large surveys, improving white dwarf candidate identification efficiency.

Findings

Identified approximately 23,000 high-fidelity white dwarf candidates.

Discovered over 14,000 new high-confidence white dwarf candidates.

Revealed that SDSS spectroscopic coverage of white dwarfs is about 40% complete.

Abstract

We present a method which uses cuts in colour-colour and reduced proper motion-colour space to select white dwarfs without the recourse to spectroscopy while allowing an adjustable compromise between completeness and efficiency. Rather than just producing a list of white dwarf candidates, our method calculates a probability of being a white dwarf (Pwd) for any object with available multi band photometry and proper motion. We applied this method to all objects in the SDSS DR10 photometric footprint and to a few selected sources in DR7 which did not have reliable photometry in DR9 or DR10. This application results in a sample of 61969 DR10 and 3799 DR7 photometric sources with calculated Pwd from which it is possible to select a sample of ~23000 high-fidelity white dwarf candidates with Teff >~ 7000 K and <= 19. This sample contains over 14000 high confidence white dwarfs candidates which have not yet received spectroscopic follow-up. These numbers show that, to date, the spectroscopic coverage of white dwarfs in the SDSS photometric footprint is, on average, only ~40% complete. While we describe here in detail the application of our selection to the SDSS catalogue, the same method could easily be applied to other multi colour, large area surveys. We also publish a list of 8701 bright (<= 19) WDs with SDSS spectroscopy, of which 1781 are new identifications in DR9/10.