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

Verbeek, Kars, Groot, Paul J., Nelemans, Gijs, Scaringi, Simone, Napiwotzki, Ralf, Drew, Janet E., Steeghs, Danny, Casares, Jorge, Corral-Santana, Jesus M., Gänsicke, Boris T., González-Solares, Eduardo, Greimel, Robert, Heber, Ulrich, Irwin, Mike J., Knigge, Christian, Wright, Nicholas J. and Zijlstra, Albert A. (2013) A determination of the space density and birth rate of hydrogen-line (DA) white dwarfs in the Galactic plane, based on the UVEX survey. Monthly Notices of the Royal Astronomical Society, 434 (4), 2727-2741. (doi:10.1093/mnras/stt1005).

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 (UVEX) survey of the northern Galactic plane, 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 DA white dwarfs with T_eff > 10 000 K (MV <12.2) of (3.8 ±1.1) × 10^-4 pc^-3, and an average DA white dwarf birth rate over the last 7×10⁷ yr of (5.4± 1.5) × 10^-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 withour determination here.

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Contributors

Author: Nicholas J. Wright

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