A determination of the space density and birth rate of hydrogen-line (DA) white dwarfs in the Galactic Plane, based on the UVEX survey

TL;DR

This study estimates the space density and birth rate of hydrogen-line (DA) white dwarfs within 1 kpc of the Sun using UVEX survey data and theoretical modeling, accounting for observational effects.

Contribution

It provides a new, calibrated measurement of white dwarf space density and birth rate based on a large observational sample and detailed correction methods.

Findings

White dwarf space density is (3.8 +/- 1.1) x 10^-4 pc^-3.

White dwarf birth rate over last 70 million years is (5.4 +/- 1.5) x 10^-13 pc^-3 yr^-1.

Results are consistent with previous estimates from other studies.

Abstract

We present a determination of the average space density and birth rate of hydrogen-line (DA) white dwarfs within a radius of 1 kpc around the Sun, based on an observational sample of 360 candidate white dwarfs with g<19.5 and (g-r)<0.4, selected from the UV-excess Survey of the Northern Galactic Plane (UVEX), in combination with a theoretical white dwarf population that has been constructed to simulate the observations, including the effects of reddening and observational selection effects. The main uncertainty in the derivation of the white dwarf space density and current birth rate lies in the absolute photometric calibration and the photometric scatter of the observational data, which influences the classification method on colours, the completeness and the pollution. Corrections for these effects are applied. We derive an average space density of hydrogen-line (DA) white dwarfs with T_eff > 10,000K (M_V<12.2) of (3.8 +/- 1.1) x 1e-4 pc^-3, and an average DA white dwarf birth rate over the last 7e7 years of (5.4 + 1.5) x 1e-13 pc^-3 yr^-1. Additionally, we show that many estimates of the white dwarf space density from different studies are consistent with each other, and with our determination here.