The luminosity function of white dwarfs and M dwarfs, using dark nebulae as opaque outer screens

TL;DR

This study uses dark nebulae as opaque screens to measure the luminosity functions of white and M dwarfs in the solar neighborhood, providing new density estimates and confirming previous findings with a novel method.

Contribution

It introduces a new approach using dark nebulae as opaque screens to determine the luminosity functions and densities of white and M dwarfs.

Findings

White dwarf density supports recent estimates.

M-dwarf luminosity function aligns with prior studies.

Cloud distances and extinctions were independently derived.

Abstract

By using dark nebulae as opaque outer screens, the luminosity function of white dwarfs and M dwarfs has been studied. High-extinction areas towards the Orion A, Serpens and rho Oph cloud complexes were observed, covering a volume corresponding to 464 pc3 in the solar neighbourhood, complete to Mv=16.5. Foreground stars were selected by VRI photometry and photometric parallaxes. The resulting foreground sample consists of 21 M dwarfs and 7 white dwarfs. The derived M-dwarf luminosity function is consistent with previous studies, showing no substantial upturn beyond Mv=16. The 7 white dwarfs imply a local density of 0.013(+-0.005)Msun/pc3 (~15% of the dynamical mass in the solar neighbourhood) supporting other recent results but obtained with a completely different method. For the clouds, foreground-star data were used to derive independent cloud distances, while the background stars and a simple model of the Milky Way gave reliable cloud extinctions.