The Luminosity Function for White Dwarfs in the SuperCOSMOS Sky Survey

TL;DR

This study measures the white dwarf luminosity function using the SuperCOSMOS Sky Survey, introducing variable proper motion limits to enhance sample size and revealing key features in the luminosity distribution.

Contribution

It presents novel techniques for selecting white dwarf candidates and provides the first large-scale luminosity function measurement from the SuperCOSMOS data.

Findings

Good agreement with previous luminosity functions

Drop in WD density at M_bol~15.75

Inflexion point at M_bol~12

Abstract

We present the techniques and early results of our program to measure the luminosity function for White Dwarfs in the SuperCOSMOS Sky Survey. Our survey covers over three quarters of the sky to a mean depth of I~19.2, and finds ~9,500 Galactic disk WD candidates on applying a conservative lower tangential velocity cut of 30kms^-1. Novel techniques introduced in this survey include allowing the lower proper motion limit to vary according to apparent magnitude, fully exploiting the accuracy of proper motion measurements to increase the sample size. Our luminosity function shows good agreement with that measured in similar works. We find a pronounced drop in the local number density of WDs at a M_bol~15.75, and an inflexion in the luminosity function at M_bol~12.