Faint Blue Objects on the Hubble Deep Field North and South as Possible Nearby Old Halo White Dwarfs

Abstract

Using data derived from the deepest and finest angular resolution images of the universe yet acquired by astronomers at optical wavelengths, with the Hubble Space Telescope (HST) in two postage-stamp sections of the sky, plus simple geometrical and scaling arguments, we demonstrate that the faint blue population of point-source objects detected in those two fields could actually be ancient halo white dwarfs at distances closer than about 2 kpc from the Sun. This finding has profound implications, as the mass density of the detected objects would account for about one-half of the missing dark matter in the Milky Way, thus solving one of the most controversial issues of modern astrophysics. The existence of these faint blue objects points to a very large mass locked into ancient halo white dwarfs. Our estimate indicates that they could account for as much as one-half of the dark matter in our Galaxy, confirming the suggestions of the MACHO microlensing experiment. Because of the importance of this discovery, deep follow-up observations with HST within the next two years would be needed to determine more accurately the kinematics (tangential motions) of these faint blue old white dwarfs.

Based on observations collected with the Hubble Space Telescope, which is operated by AURA, Inc., under contract with the National Science Foundation.