A catalogue of white dwarfs in Gaia EDR3 (2106.07669v2)

Abstract: We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung-Russell diagram. We then used a sample of over 30 000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS) to map the distribution of these objects in the Gaia absolute magnitude-colour space. Finally, we adopt the same method presented in our previous Gaia DR2 work to calculate a probability of being a white dwarf (Pwd) for $\simeq$1.3 million sources which passed our quality selection. The Pwd values can be used to select a sample of $\simeq$359 000 high-confidence white dwarf candidates in the magnitude range 8< G <21. We calculated stellar parameters (effective temperature, surface gravity, and mass) for all these stars by fitting Gaia astrometry and photometry with synthetic models. We estimate an upper limit of 93 per cent for the overall completeness of our catalogue for white dwarfs with G $\leq$20 mag and effective temperature (Teff)>7000K, at high Galactic latitudes (|b|>20{\deg}). Alongside the main catalogue we include a reduced-proper-motion extension containing $\simeq$10 200 white dwarf candidates with unreliable parallax measurements which could, however be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS DR16 spectroscopy and provide spectral classification based on visual inspection for all resulting matches.

Overview of the White Dwarfs Catalogue in Gaia EDR3

The paper "A catalogue of white dwarfs in Gaia EDR3" by Gentile Fusillo et al. presents a comprehensive catalogue of white dwarf candidates derived from the Gaia Early Data Release 3 (EDR3). Utilizing advanced selection criteria based on absolute magnitude, color indices, and quality flags from Gaia, the authors filtered the dataset to retain objects predominantly located within the white dwarf locus on the Hertzsprung-Russell (H-R) diagram. This paper significantly expands the scope and accuracy of previous catalogues, offering crucial insights into the population and characteristics of white dwarfs.

Methodology

The authors began by defining a broad locus in the Gaia H-R diagram that demarks where white dwarfs are likely found. They excluded objects with unreliable measurements using multiple criteria drawn from Gaia data quality flags. To address potential contamination, the paper relies heavily on a sample of over 30,000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS), mapping their location in Gaia's magnitude-color space.

Following the assembly of a refined selection of approximately 1.3 million sources, they calculated the probability of being a white dwarf ($P_{\rm WD}$) for each star, thus enabling the identification of ~359,000 high-confidence white dwarf candidates. The inclusion of stellar parameters such as effective temperature, surface gravity, and mass was achieved through Gaia photometry and astrometry, employing synthetic atmospheric models.

Key Results

• Completeness: The overall completeness for identifying white dwarfs with $G \leq 20$\,mag and effective temperatures greater than 7000\,K is estimated at 93%, particularly in less crowded regions.
• Stellar Parameters: Parameters for effective temperature, surface gravity, and mass for the identified white dwarfs were derived using well-established atmospheric models, employing corrections for interstellar extinction based on modern 3D maps.
• Improved Sample Size: The EDR3 dataset provides an increase of almost 100,000 new white dwarf candidates compared to DR2, attributed largely to improved detection in densely populated regions and increased faintness depth.
• Variability Indicator: An excess flux error parameter is included to flag potential intrinsic variability, with many cataclysmic variables showing significant variability profiles within this metric.

Implications and Future Research Directions

The enhanced catalogue serves as a critical resource for understanding the stellar evolution path and characteristics of white dwarfs, which are essential for various applications from flux calibration to exoplanetary research. The increased sample size offers broader statistical consideration of white dwarf properties, aiding studies in chronological aspects of stellar evolution and potential mechanisms behind cooling delays.

For future developments, the paper sets the stage for extensive spectroscopic observations of Gaia white dwarfs, pivotal for examining their atmospherical properties and refining mass-radius ratios. With the advent of next-generation observatories like the Vera Rubin Observatory, further refinements in faint object measurement will likely enhance the depth and quality of subsequent releases. Additionally, this catalogue paves the way for detailed studies into binary systems, especially those involving white dwarfs as potential end-states in stellar lifecycle models.